My 05 Envoy has no ballz. 0-60 times horrible!

[Voymom]

@ Voymom - where oh where do I start with you?

You've provided me with so much material, I could do a comedy tour for a year, and not repeat the same joke twice - kinda like Jeff Foxworthy's redneck jokes.



Noted, tyvm



LOL ;-) even though I had to Google it for verification, there's no disputing your math there! I guess my point was having watched it several times, in my opinion the starting point was something just after the 3s mark (video time), and the end point right around 13. I agree it's hard to gain consensus on the exact points, especially from a youtube video, which is why I opened it up for other commentary.

And actually if you watch and listen closely, you can hear Mat hit the throttle just after the DIC time turns over to 14s. Do this: Start at the beginning of the video, and hit the play button. Now as FAST AS YOU CAN, hit pause and look at the DIC timer...repeat this until the very first instant you see the timer display 15s - and you will see the speedo already reads almost 10mph. In video 1, we were able to see the tach needle move by the same method. In my opinion that's the instant we all have to start the timer for comparison.

At the 60mph mark, what I did was watch for the needle to hit 60 square on, and hit pause as fast as I could. Almost every time, the very next frame I see when I hit play the DIC timer turns over to 14s...average human reaction time is pretty close to a quarter second...but if you repeat the excercise several times they will tend to cancel each other out at the beginning and end. So what I see is "just after 14s" to "just before 24s" - so a little more than 9, a little less than 10, for the moment I'm happy to split the difference and call it 9.5 if you're ok with that.

So let's revisit video 1 with the same methodology, except there we use video timer, timed to first instance of detectable tach needle movement: I can repeatedly stop the video showing the tach at ~900rpm, while the video timer is STILL displaying 1s - every time I get it stopped there, the very next frame shows the video time turn to 2s. So this is the starting point here. Those of you from Missouri may appreciate the screen capture:

View attachment 9545

Doing the same at the other end I consistently get the video to stop just as it hits 12s - but the speedo shows a tad under 60mph. Missourians now know better than to doubt me, so this is for stubborn Michigan moms only:

Check your approx. 900RPM again, because it actually shows the needle a smidge over 1k RPM

View attachment 9546

I leave it for judicious students to verify that this means the 0-60 run in video 1 took a tiny shade more than 10s...I'll be friendly and not argue for those last couple tenths, let's call it 10s even.

I will agree and say 10s on the first run, as I stated below the quality of the 1st video for me is poor, so I could not get an actual opinion/time range on it

Time difference between run one and run two where hypothetically temp was the only changed variable (oh and ~ 75lbs of gas)?

Actually 75lbs of gas can be argued here, my fuel level sender is bad...for all we know we had a 1/4 tank and not a 3/4.

ZERO POINT FIVE SECONDS! {Slightly less actually, because I can show (yeah, just trust me now) that run 2 was 9.8s and run 1 was 10.2, or 0.4s}

That's fine - I always conceded some allowance for some effect due to temperature. I hope now though that you get my earlier point that your perception of the change is a fair bit magnified from the reality.

It may be magnified, but my point was that Temperature DOES play a difference, albeit small, but there is one. Which is why a lot of people do their 0-60 tests at night opposed to the day.

But Mat said 10 - are you arguin with him or with me? Better be him cuz I can back it up baby!

I'm not arguing with anyone, Mat has the right to hold a difference of opinion from me, and vise versa, as does everyone else

LOL goofball. What's "the right way"? There's ONLY ONE right way - the way that yields the correct answer. Just so happens to coincide with MY WAY! hehehehe

I stated "the right way" simply because had he watched it that way he would see where I was getting my answer from. I am always open to adjustments and being corrected, I am not always right and can admit that. The way I watched it simply and stating the way I watched it was to simply show how I got the results I did.

So when you watched it again, the time changed from 9s to 8s? Or did you just do it "the right way" the second time? LMFAO And now run 1 has a range of "10 - 12" vs previously stated "11-12"??? Mat came in and saw you typing, realized you were disagreeing with HIM and made you change it, didn't he? C'mon admit it!

No, Mat didn't make me do anything, I did it on my own accord. I gave myself a 10-12 instead of 11-12 allotment because the quality of the video is difficult for me to see and hear.

Nooo oh no not at all. {Psssssst Mat, can you still get your money back for the ring and cancel the hall?}

Absolutely uncalled for. And extremely hurtful.

 

[WarGawd]

Why dont you all get the tourqe app and use the 0-60 function in that to get to compare apples to apples??.

Yes, that would be far better and easier than trying to analyze video. But since a lot of people don't want to or can't afford to invest in a scanner (still needed to use Torque), we'd still like to be able to find value in the videos people have made an effort to make & upload. Plus Torque is android based, not everyone has android phones...still, whatever basic software that came with the scanner could probably be used just as well to get very good comparison data - they are all monitoring the same basic info.

Every car i had was always running much better like after a summer afternoon rain after the temperature fallen like 10C and the air is slightly moist and more dense and full or oxygen, especially the turbo cars i had.
Nothing strange with that, cooler air = more oxygen hence the INTERCOOLER.

Granted. Even I will concede I notice differences in differing weather. I mean there are days when I would absolutely swear my vehicles ran better/smoother/happier just from spending a half day doing a full wash/wax/detail job. So I hope it's coming across that I am not disputing claims of minor (ie up to 1/2 second) differences in 0-60 times. OTOH hand CaptainXL has reasonably well documented a full 3 second change while the only changed variable he can think of is the temperature. It's inexplicable to me that temp alone can account for that.

Also cooler air/more oxygen = more power isn't the complete story there - the other side of that is that the lower intake air density allows/encourages the addition of slightly more fuel to maintain the right mixture - together they create power increases in cooler air. Without adding more fuel, adding more air/oxygen is redundant, since the A/F mixture is already supposed to be close to ideal (where ideal means just enough air to completely burn the fuel). With no extra fuel to extract energy from, no power increase can be had.

twocents

Warmer air would lead to preignition if I am not mistaken and the pcm would retard timing. This is exactly the type of thing that it seems to be...ignition related. I am going to try some premium gas and see what happens. I think this might lead somewhere.

That's not my understanding. PRE-Ignition is an unwanted effect of the air-fuel mixture exploding before the ideal time for the conditions. Warmer air will lead to a reduction of density, the PCM will react by adjusting the air-fuel mixture towards it's ideal ratio of 14.7:1. That adjustment is fairly quick, the short term fuel trim (STFT). Since the fuel mixture is still "ideal" there's no expectation that the mixture should explode with any different timing.

Going from 100F to 30F, air density increases by about 14%. To maintain the same mixture ratio, we need to increase the fuel by the same proportion. The ideal gas law always relates Pressure, Volume and Temperature of a gas (actually anyone who knows their thermodynamics would disagree on a technicality, but they'd agree it's a very good approximation most times. Kinda like how we don't have to consider special relativity at most of the speeds we humans travel {interesting trivia, the GPS satellite network DOES need to consider relativistic terms or it wouldn't work}) Anyway, IF the engine was 100% efficient, we would extract 100% of the extra energy of this added fuel. We could closely approximate the time difference on a 0-60 run as a 14% improvement, on temperature alone. For a vehicle that does 14s at 100F, the reduction would be close to 2s (14% of 14s =1.96s). HOWEVER modern gasoline engines are only 25-30% efficient. We only get that much improvement from the added fuel. The rest is wasted as heat(exhaust, radiator, tranny, tires etc). Again, the simplifying approximation might suggest we'd only gain about 25-30% of that 1.96s - pretty close to a 1/2 second.

There may be an argument for the PCM to retard timing with COLDER air as follows: PV=nRT is the gas law I mentioned. The volume of air/fuel taken in at BDC on the compression stroke is fixed, but it's density it's 14% higher. Now approaching TDC, the greater initial density gives rise to a greater gas temperature just prior to ignition spark. It is this temperature increase that may give rise to premature ignition but the actual temperature at this point is somewhat offset by the reduced starting temp on intake. I'd be purely guessing at this point to say how much that offset is, but it makes preignition less likely. IF this is detected by the knock sensors (essentially tiny microphones) then yes the PCM will react to that and retard timing. If not, then no adjustment needs to be made.

I approached this from the opposite view (colder air), and preignition seems possible but unlikely. Similarly normal environmental increases in intake air temp would reduce density, reduce fuel injected, have a lesser temperature increase from BDC to TDC, but that is again offset to some unknown degree by the higher starting temp. Again, not likely to result in a condition where the PCM has to alter ignition timing to compensate.

So, feel free to run a tank of premium...by the end of that any PCM knock compensation should have trended back towards normal, if not completely disappeared. Then do a run and capture it somehow. Intuition and semi-educated guessing on my part suggest you won't see a change.


The articles below all surfaced while I was trying to understand and better explain my original contention that temperature difference alone does not explain YOUR observation. Anybody interested in this thread might be well served by scanning thru them, though some are pretty involved.

In no particular order:

What are fuel trims all about? <---- really good one

Engine efficiency

Air - Temperature, Pressure and Density

Air-fuel ratio

Ideal gas law

Octane rating

Horsepower vs torque

Torque

 

[Harpo]

 

[CaptainXL]

I follow this thread because i have the same problem.
"..."
And a lot worse mpg than a year ago, now 14.3mpg average mostly highway

We don't have the same problem. My engine gets 18 mpg.

 

[WarGawd]

@Phantom and Voymom

Seriously??? Overreact much?

If you take exception to my comment(s) I'd have no issue engaging in a debate via PM or somewhere over in O/T perhaps. Set it up as a poll even: Is WarGawd an A$$hole, or Funny? I strongly suspect the results and replies will be roughly divided as they were in Jkust's http://gmtnation.com/f33/would-piss-you-off-3757/ thread.

In any event let's let CaptainXL get his thread back on topic, and we'll keep our disagreement out of it, OK?

 

[CaptainXL]

No need to erase your post. I welcome all comments.

 

[gmcman]

Have you tried some ethanol-free fuel yet? Seems to be a few places in your area and (Sparta Municipal Airport) being one of them.

9100 Vinton Ave Sparta, Michigan 49345 - (616) 887-5744

Here's a list from Pure-Gas:

Ethanol-free gas stations in the U.S. and Canada

Keep in mind our ECM learns a fuel table with each fillup of something like 7 gallons or so, not sure how much. Now AFAIK, to make it easier to adjust parameters for cold start, warm start, hard accel, light accel, etc...if the ECM detects low octane fuel then the parameters are narrowed to allow for faster adjustments from info collected from the sensors. When you fill up, the ECM allows for the possibility of more ignition advance and gives you a set time to see if the tank was filled with higher octane.

If there continues to be knocking from pre-ignition or detonation then it will lower the max ignition advance per given driving situation, this process will reset after you fill up again.

With that being said, if you fill up and go stomping on the pedal right away, you might get the lower octane table for the entire tank. Take it easy until the fuel gets through the lines first.

This is how I learned it and I'm not completely 100% on the newer models.


Nice write-up BTW WarGawd

 

[CaptainXL]

I will give it a shot. There is a station on the east side of town that has 94 octane.

 

[neelskit]

@Phantom and Voymom

Seriously??? Overreact much?

If you take exception to my comment(s) I'd have no issue engaging in a debate via PM or somewhere over in O/T perhaps. Set it up as a poll even: Is WarGawd an A$$hole, or Funny? I strongly suspect the results and replies will be roughly divided as they were in Jkust's http://gmtnation.com/f33/would-piss-you-off-3757/ thread.

In any event let's let CaptainXL get his thread back on topic, and we'll keep our disagreement out of it, OK?

I believe that most people would have taken offense to your post, so if you didn't want a disagreement, then you should have kept your post to relevant information rather than insults and sarcasm.

Moving right along...

I, too have been having the same issue as Captain, sluggish performance- more pronounced with warmer temperatures. With the A/C on, the truck is just plain slow. It has been that way since I bought it and I have had it looked at by the dealer only to be told it is operating within specs. I got the opportunity to drive my brother-in-law's 2003 TB EXT (same as mine except he has a G80 and I don't- both I-6, 4X4, with 3.73s) and his by far had better acceleration. I brought up the IAT sensor because that is about the only sensor I still have on my truck that is stock. I agree that ambient temperature should not make this big of a difference, but if the PCM is getting false data from an intermittent sensor, then it is setting timing and fuel trims based on bad information. However, based on the info provided by Captain and C-ya, this issue doesn't appear to be caused by the IAT sensor. A +30F over ambient temperature is not out of line on a hot day. Mine also has an intermittent hesitation when accelerating from a stop and again, has had this issue since I bought it, and of course, the dealer could never replicate the problem. All maintenance is current, no codes present, 174k miles.

 

[CaptainXL]

This seems like a long shot. But does GM know before coming off the assembly line which dealer will get the truck? If thats the case then could there be some profiling where the PCM is tuned to run best in the type of environment in which it will ultimately be sold? Ex. Sold by a dealer in a northern state therefore it is tuned to run better in the cold? Something to ponder.

 

[Denali n DOO]

I believe that most people would have taken offense to your post, so if you didn't want a disagreement, then you should have kept your post to relevant information rather than insults and sarcasm.QUOTE]

You just did what you posted not to do ? Come on guys and gals, this is a really good thread, don't spoil it. Let Sleeping Dogs Lie.....send some PM's if you have comments not related to this thread topic. I'm very interested in the outcome of Captain XL's situation rather than judging a popularity contest...

 

[WarGawd]

I feel temp does indeed play a role, not a terribly huge one but it's definately a factor... anyone who has flown planes can attest to this. Warm humid days compared to cool days is a huge difference in terms of performance and climb rate. The higher the density altitude, the less performance you can expect.

I had wanted to come back to this earlier. You're exactly right. It was the aviation guys who first started playing with the concept of Density Altitude, so they could make adjustments when taking off at higher, hotter airports. Part of the reason DA may have a bigger impact on them, is that for them it doesn't just affect engine performance - it's a big factor in wing (ie lift) performance. And in support of something else you said about two vehicles running differently in two different states, that's true as well. Racers later adopted and improved on the concept, so that they could apply a correction factor to their run times in one place and compare it with a weather corrected run elsewhere, to see if they were running as expected at that particular time & place. The intent was to eliminate some of the variables that give rise to time changes, so they could better focus on the variables they could control (tires/shift points/carb jetting etc etc) When you look into it, DA accounts for pressure/temp/ and I didn't realize, but humidity as well. And it turns out that atmospheric pressure is a more significant factor than temperature in the big picture, all tied in with that PV=nRT relationship I spoke of previously.

Drag Times has decent online DA calculator here. Note the availability of iPhone and Android app there as well. Although it's for correcting 1/4 mile times, it shouldn't be a huge stretch to play with it to get a feel for how 0-60 times would be affected by temp (or even humidity and pressure differences).

I'm not going to take that much further - I think we can all agree that reasonable temp differences, minor changes in pressure and humdity, minor weight changes are all kinda buried in the "noise" somewhere. Even if it's not directly applicable here, people can play with that calculator and develop an intuituve feel for the magnitude of the effects (except weight)

@neelskit, gmcman, Captain and C-ya. We've all contemplated and commented on possible IAT flaws possibly playing a role in Captains seemingly sudden and large change. Turns out the IAT is a simple thermistor, seems to play a secondary role to the MAP sensor in setting fuel mix and timing, and can (should) generate codes if reported IAT temps are over or under expectation. Regardless of how that's accomplished (by calibration with the OAT/ambient temp sensor or otherwise), Captain (and seanpooh) doesn't have any codes, and C-ya's IAT monitoring suggests both are working the same. It isn't looking like IAT is the culprit for CapXL. Maybe even neelskit can swap his stock one with the one in his friend's better running TB, just to see what happens

@ CapXL - I'm jealous of your gas mileage - can you elaborate a bit if the 18mpg is city/hwy/combined? I know I'm kind of heavy on the pedal as I always seem to be in a hurry, but comment briefly on what kind of driver you are? And what I'm most curious about, is the 18mpg seemingly consistent across this observed seasonal performance change? Not sure if you drive it enough/track it enough to be definitive, but I have to wonder out loud what's going on if your mileage never changes between "good performance in cool temps" vs "sluggish in the summer" . You'd think it would have to show up somehow.


@CapXL : may not be the most helpful answer but I'll throw it out there for you to chew on: When shipped from factory, the rear view mirrors with compass are set for compass variance Zone 8 - if you move it to California or drive it cross country the manual suggests resetting the variance zone per the map supplied in the manual. Seems to me if they were setting up the PCM for region specific operation, they might also set the compass zone, it's literally a 10 second operation. OTOH they ship 'em with Onstar and XM radio packages, but no cabin air filter and rear diff drain plug...

Oh and lastly @ Harpo - you deleted your post just as I was trying to reference it. Thought I spotted that you had Torque app as well, maybe you can track down that same HP measurement that CapXL has done before and throw it in to the mix.

I know I'm gonna sound like a broken record, but to me these things are all still looking at the power production side of the picture. A few days back I had a fleeting thought about a temperature related tranny issue that I thought was a possible candidate for something that might not throw codes, but I got sidetracked and lost my train of thought...it was triggered by something I read, so I'm hopng it comes back to me

HAGD all

 

[WarGawd]

This is not the same thing I read that prompted my earlier, now forgotten thought, but I spotted this in the transmission troubleshooting manual (scanned pdf) from the collection I downloaded from MooseMan:

View attachment 23112

Might be someething to consider, as it seems to fit the general description of things prior to the return to better performance.

Similarly, there seems to be something that might offer an avenue to pursue for seanpooh, whose truck seemed to drag ass later on. Even though his tranny was rebuilt, he never did answer my questions about the rebuild:

View attachment 23113

This was on 24th page under a heading of Torque Converter Diagnosis Procedure, from the transmission troubleshooting manual that Mooseman has collected in a big zip file called 2002-05_TB_Service_Manuals

 

[CaptainXL]

@ CapXL - I'm jealous of your gas mileage - can you elaborate a bit if the 18mpg is city/hwy/combined? I know I'm kind of heavy on the pedal as I always seem to be in a hurry, but comment briefly on what kind of driver you are? And what I'm most curious about, is the 18mpg seemingly consis

I usually get about 11-13 city depending on if I am aggressive at times or not. I get 18 mpg on the hwy in the summer. Winter gas mileage seems poor. Using more fuel obviously. Almost seems like I am running rich. Never had the chance to get mpg data during the winter. Good observation on your part.

I would characterize my driving style as conservative. I usually go 5 mph over speed limit and keep up with most traffic. I can't be too conservative with the throttle because the truck lacks some of it's low speed torque which I attribute to the 3.42 rear. I almost always set cruise at 70-73 mph. I hardly ever go above 75.

While driving in the city when I takeoff from a red light it seems almost like the trans is in 2nd. Hot weather usually means poor torque off the line. Cool weather and it's sporty and the trans shifting seems crisp.

 

[WarGawd]

While driving in the city when I takeoff from a red light it seems almost like the trans is in 2nd. Hot weather usually means poor torque off the line. Cool weather and it's sporty and the trans shifting seems crisp.

I think I read your reply before that edit. The same T/S manual had procedures for diagnosing issues of that nature too (ie wrong gear selection). But I think it would be really obvious from vehicle speed at shift point whether you had been in first or 2nd - 6100 rpm shift from 2-3 would have you at 90mph remember. And I wanted to mention that when Torque converter stall tests were mentioned earlier in the thread, Chickenhawk had some cautions about that. But there is a stall test described in that manual as well, and AFAIK it's a GM manual so it seems sanctioned by GM in some manner at least.

Mileage figures on highway are comparable to mine. My city mileage sucks but I know why that is for the most part. I do know my t-stat is going bad, running cool on occasion, but it has been intermittent and infrequent enough that I don't suspect it to have hurt my mileage much - replacement is scheduled, parts in hand. It would be a nice surprise if a changeout did give me back a couple mpg.

 

[CaptainXL]

So this morning I took the truck out and had my scan tool connected. It was 60 out and it ran ok. I looked down at the scan tool and I noticed that #6 cylinder is misfiring again not just at idle. So I looked at my 0-60 time and it was 11.5 seconds. So I am now going to start looking into that issue first before continuing.

 

[Hypnotoad]

I haven't read the whole thread because it has become pretty long, but have you ever suspected the torque app as being the problem? It uses GPS to determine distance in some instances, which isn't all that accurate on a smartphone. Did you double check all the info in the vehicle profile?

Are you using a cheap Bluetooth adapter off ebay? I've noticed that the info from the computer has some lag when you use the cheap adapters too.

Just something to think about.

 

[CaptainXL]

I haven't read the whole thread because it has become pretty long, but have you ever suspected the torque app as being the problem? It uses GPS to determine distance in some instances, which isn't all that accurate on a smartphone. Did you double check all the info in the vehicle profile?

Are you using a cheap Bluetooth adapter off ebay? I've noticed that the info from the computer has some lag when you use the cheap adapters too.

Just something to think about.

??? What does distance have to do with 0-60 time? It's using vehicle speed sensor data.

 

[Hypnotoad]

??? What does distance have to do with 0-60 time? It's using vehicle speed sensor data.

That's true. All I'm saying is that in general, I don't feel that the Torque app is all that accurate. Have tried measuring it other ways?

 

[CaptainXL]

That's true. All I'm saying is that in general, I don't feel that the Torque app is all that accurate. Have tried measuring it other ways?

Im pretty confident using Torque and I would say it's very accurate.

 

[Hypnotoad]

http://www.moderncamaro.com/forum/v6-engine-discussion/29034-v6-0-60-performance.html

Check out post #9. The guys 0-60 times were 2 seconds slower with Torque compared to a Matrix Accelerometer.

If you keep reading it turned out his real time was somewhere in the middle.

 

[CaptainXL]

V6 0-60 performance - ModernCamaro.com - 5th Generation Camaro Enthusiasts

Check out post #9. The guys 0-60 times were 2 seconds slower with Torque compared to a Matrix Accelerometer.

If you keep reading it turned out his real time was somewhere in the middle.

Again. 0-60 times have nothing to do with Torque. If you have useful info I welcome it. Stop frustrating me with useless info.

 

[Hypnotoad]

Again. 0-60 times have nothing to do with Torque. If you have useful info I welcome it. Stop frustrating me with useless info.

You're using the Torque app with a cheap elm 327 adapter, am I wrong? I just think it's possible you're truck is going faster than what Torque says.

http://torque-bhp.com/forums/?wpforumaction=viewtopic&t=2089.0

Straight from the mouth of the creator of Torque.

 

[WarGawd]

You're using the Torque app with a cheap elm 327 adapter, am I wrong? I just think it's possible you're truck is going faster than what Torque says.

Forums &mdash; » Torque OBD ECU Scanner » Torque Discussion / Ideas » 0-60 times 1/4 timesTorque

Straight from the mouth of the creator of Torque.

My read of that thread suggests the OP in that case concluded he needed to modify his approach to using the app, and that Torque itself was very accurate for speed because it was directly using OBD data (unless that was somehow unavailable, whereby GPS would become the next most accurate auto selected method)

What you may be unaware of, based on your previous mention that you hadn't read the whole thread, is that CapXL 0-60 times at the outset of the thread and subsequent ones were based on video timed results - Torque didn't enter the picture for timing. Initially he had what he felt was sluggish performance, did a video to demonstrate it, and more recently as fall approached, another video to show the significant improvement. THEN he did another run while monitoring stuff with torque as he continued to investigate, and noticed poorer performance in conjuntion with a misfire on 6. While he may have recorded a 0-60 run time of 11.5s to show the magnitude of the performance hit, I don't think it was made clear whether he used Torque for the timing or some other method - and it's probably irrelevant IMO, because I suspect he was just trying to convey something like "it used to suck, then it got better, and now it got worse again".

Anyhow, Cap - was just wondering if you'd gotten around to putting the premium in the tank before you did that run with the scanner? What else were you monitoring, were there any other observable changes , and were you logging to file/uploading it, or just displaying real time data for observation? Oh and refresh my memory, too rushed to look back in the thread - what was the cylinder where you found the corroded coil pack?

 

[CaptainXL]

I suspect he was just trying to convey something like "it used to suck, then it got better, and now it got worse again".

Yes, that is exactly what I was trying to convey.

Anyhow, Cap - was just wondering if you'd gotten around to putting the premium in the tank before you did that run with the scanner? What else were you monitoring, were there any other observable changes , and were you logging to file/uploading it, or just displaying real time data for observation? Oh and refresh my memory, too rushed to look back in the thread - what was the cylinder where you found the corroded coil pack?

Haven't gotten to the point of filling up with 94 octane. Waiting until im empty.

I made a log file and I attached it here. The speed is in meters/sec to will need to convert to mph in excel.

The corroded coil pack was #4. Will check the rest again as well as the wires to #6. There are three wires going to each coil. I should be able to see if I have a nice 12 volt signal at each of them with the koeo. They are the pink wires according to my electrical schematic. Just gotta get some time to troubleshoot closer and see if the coil or injector is bad/stuck. I am not gonna proceed any further with 0-60 testing until I get the misfire issue situated.

When I use torque I set it up to monitor the vitals such as engine vacuum, voltage, timing, speed, misfires and CTS and IAT temps. I also check throttle position and such but Im pretty sure the throttle is working as designed.

 

[Hypnotoad]

This thread is over 180 posts long, and I've only been casually following it. Sorry, I didn't realize you were using something other than Torque to time your 0-60.

Good luck figuring it out.

 

[WarGawd]

I made a log file and I attached it here. The speed is in meters/sec to will need to convert to mph in excel.

<snip>

When I use torque I set it up to monitor the vitals such as engine vacuum, voltage, timing, speed, misfires and CTS and IAT temps. I also check throttle position and such but Im pretty sure the throttle is working as designed.

Hmm, I think you may have snagged the wrong log file for inclusion in the .zip?? I also opened it with Wordpad as a text file just to verify that there was no weird demlimiting going on, but these are the only headings present in that log file, all seemingly based on data picked from the phone, but no OBDII type data PIDs:

GPS Time / Device Time / Longitude / Latitude / GPS Speed (Meters/second) / Horizontal Dilution of Precision / Altitude / Bearing / G(x) / G(y) / G(z) / G(calibrated)

The date and time seems to agree with when you said you collected it yesterday morning, so I'm guessing there's another log file somewhere

 

[C-ya]

This may be why there is no relevant info in the file. From the Torque forum from piemmm (the developer):

Have you told the app what sensors to log (Go to the main app settings->Logging/Data upload->Select what to log) which will then give you the chance to add which sensors are relevant

The logfile by default records GPS and accelerometer data (then what sensors you have selected in the ‘Select what to log’ setting option). You can then export all of this data as CSV or KML formatted data

Which screen are you in when you are sending the log? – the Realtime information screen is the one that sends the acutal logfiles, and you’ll need to send them as CSV if you don’t want them converted into track files.

With the CSV file format, you’ll be able to import the data into a spreadsheet and play with the numbers

 

[CaptainXL]

Ok I got the right pids selected for the log in torque. I started driving yesterday and noticed 44 misfires as I got underway. While on the highway and subsequent full throttle accelerations it noted no additional misfire. Using 94 octane at the moment.

Noticed a slight perceptible increase in power using the 94 vs 87 octane. Perhaps it was psychological. Drove 300 miles yesterday and noticed no issues. Did not do any 0-60 runs but getting off the ramp onto the highway seemed good acceleration wise.

Starting to wonder if this Costco gas I have been getting has something to do with it.

 

[WarGawd]

Ok I got the right pids selected for the log in torque. I started driving yesterday and noticed 44 misfires as I got underway. While on the highway and subsequent full throttle accelerations it noted no additional misfire. Using 94 octane at the moment.

Noticed a slight perceptible increase in power using the 94 vs 87 octane. Perhaps it was psychological. Drove 300 miles yesterday and noticed no issues. Did not do any 0-60 runs but getting off the ramp onto the highway seemed good acceleration wise.

Starting to wonder if this Costco gas I have been getting has something to do with it.

Bullet point questions:

- 44 misfires all on #6?
- you plan to upload a new log?
- misfires observed last time were under load, not the idle misfires that you had discounted from longer ago based on the TSB info?
- you had changed out all the coilpacks previously, or just the corroded one on #4 (I can't recall, may be mentioned in another thread)?
- When I did my plugs, I left the coilpacks connected, and I ended up getting the #5 pretty twisted up - didn't seem to affect me, but maybe you had something similar happen on #6 where you loosened a wire in the connector plug?

Lastly, kinda hard to phrase this, but I'm having a mental lapse trying to get my head around something - lemme ramble a sec. Throughout this thread you have mentioned that one of the puzzling things about this perf. problem is that you weren't seeing any codes. Then you got the scanner/Torque and started looking a little deeper. At various times you noticed misfires. My understanding then is that previous to the scanner these misfires weren't manifesting themselves via any dashboard MILs, and now that they are observed using Torque they still do not generate any MILs on the dash (or thru the DIC) and that they also effectively clear themselves when the condition is no longer detected for a while - would that be correct?

Oh and I wouldn't mind reading that TSB - got a decent link for reference?

Cheers

PS - better performance w/ 94 vs 87 - prob temperature/humidity/increased sunspot activity related hehehehhe lmfao (j/k, all I'm saying is it's hard to establish cause/effect)

FYI I found a post where the Canadian supplier of Costco gas is mentioned, Googling might give you some basis for arriving at a pro or con opinion where you live

 

[CaptainXL]

Bullet point questions:

- 44 misfires all on #6?

Correct. I have no misfires on any other cylinder over hours/days and months that I have observed.

- you plan to upload a new log?

Yes.

- misfires observed last time were under load, not the idle misfires that you had discounted from longer ago based on the TSB info?

Hard to say. #6 seems to misfire mostly before the first 5 minutes of driving from what I can see. But that's not to say I don't see misfires at any other time. Will need to check a bit further. The misfires come and go in spurts. You will be able to see in the log.

- you had changed out all the coilpacks previously, or just the corroded one on #4 (I can't recall, may be mentioned in another thread)?

I just changed out #4 due to corrosion. I swapped 6 with 3 about 1 month ago to rule out a bad 6 coil.

- When I did my plugs, I left the coilpacks connected, and I ended up getting the #5 pretty twisted up - didn't seem to affect me, but maybe you had something similar happen on #6 where you loosened a wire in the connector plug?

No. I disconnected each primary wire connector for all coils.

Lastly, kinda hard to phrase this, but I'm having a mental lapse trying to get my head around something - lemme ramble a sec. Throughout this thread you have mentioned that one of the puzzling things about this perf. problem is that you weren't seeing any codes. Then you got the scanner/Torque and started looking a little deeper. At various times you noticed misfires. My understanding then is that previous to the scanner these misfires weren't manifesting themselves via any dashboard MILs, and now that they are observed using Torque they still do not generate any MILs on the dash (or thru the DIC) and that they also effectively clear themselves when the condition is no longer detected for a while - would that be correct?

Yes this is correct and it is the proper thing for the PCM to do if i understand it's operation. To an unknowing layperson, on the surface it seems very strange. There are two counters per cylinder (two pids). One is for CURRENT MISFIRES and the other is MISFIRE HISTORY. The misfire history (which I am assuming totals all of the misfires under certain operating conditions) will add up. I have zilch/zero in that total. So maybe this is all for not and I am chasing a rabbit.

Oh and I wouldn't mind reading that TSB - got a decent link for reference?

I can look it up. I posted it in one of my earlier threads a few months back.

PS - better performance w/ 94 vs 87 - prob temperature/humidity/increased sunspot activity related hehehehhe lmfao (j/k, all I'm saying is it's hard to establish cause/effect)

Very well could be due to cooler temps outside. Like I said, it was probably psychological.

 

[WarGawd]

Correct. I have no misfires on any other cylinder over hours/days and months that I have observed.

So that should be P0306 right? Any other codes associated with it (not sure they'll show up in the log)?

Hard to say. #6 seems to misfire mostly before the first 5 minutes of driving from what I can see. But that's not to say I don't see misfires at any other time. Will need to check a bit further. The misfires come and go in spurts. You will be able to see in the log.

Yes this is correct and it is the proper thing for the PCM to do if i understand it's operation. To an unknowing layperson, on the surface it seems very strange. There are two counters per cylinder (two pids). One is for CURRENT MISFIRES and the other is MISFIRE HISTORY. The misfire history (which I am assuming totals all of the misfires under certain operating conditions) will add up. I have zilch/zero in that total. So maybe this is all for not and I am chasing a rabbit.

Ok great, very helpful. And based on some reading I did when I got my first P0128, my impression seems similar to yours - there may at times be a condition detected by the PCM, which it does not report to the driver via MIL/CEL(/DIC?) immediately. Instead it will hold off and more or less attempt to verify that the detection was real.

Anyway, so I wandered off looking for a better understanding of the distinction between "misfire" and "knock", how misfires are detected etc. Hard to decide exactly how to condense a couple hours of reading to put here to help you and future readers vs bloating this post but....I'm gonna try summarizing what I thought was relevant in drawing my conclusion below.

- misfire detection is driven by OBD emissions requirements, misfires cause greater emissions, and potential damage to converters
- newer (2010+) techniques for misfire detection have a much better detection ability with much lower false detection rate, nevertheless the method likely used in our trucks is easily sufficient for accurately detecting single cylinder misfires
- we can safely assume the misfires you detected are "real", but if they are massively more prominent when cold they may not be
- no cylinder fires 100% of the time under all load conditions - a few misfires here and there aren't unexpected, but it's reasonable to expect them to be randomly distributed
- since it's based on crank rotational speed variations, some pretty spurious stuff can cause false detections
- quoting a couple paragraphs from Analyzing Ignition Misfires

When the OBD II system detects a misfire, it stores operating data such as engine speed, load and warm-up status. While the misfire is happening, the OBD II system is supposed to flash the MIL lamp once a second to alert the driver. Because this might distract the driver from her cell phone conversation, sipping her Starbucks coffee or yelling at her kids in the back seat, the OBD II system will set a temporary misfire code after the second such occurrence. From that point on, the MIL lamp should flash every time the misfire returns. If the same thing happens on the next trip, the MIL lamp should blink as before and remain on even when the misfire ceases.

If the misfire problem has gone away and does not recur on the second or following trips, the OBD II system may erase the temporary misfire code and forget the entire episode. The code may also be erased if no misfires are encountered under similar driving conditions during the next 40 drive cycles.

Knowing this, you should always look at the history freeze-frame data when diagnosing a misfire code. If the code was set when the engine was cold, chances are the OBD II system is being overly sensitive and there is no real misfire problem. Check for any technical service bulletins (TSBs) that may be out on the vehicle for false misfire codes. The cure, in many instances, is to flash reprogram the PCM so the OBD II system will be less sensitive to misfires.​

Also you've made no prior mention of any observed plug fouling on 6, nor of noticing any odor from the tailpipe (both would speak to the relative longterm condition of a consistent misfire that would be dumping unburned fuel, and which probably would have affected the cat converter by now & more or less eliminated by the backpressure test). You've never mentioned any excessive oil consumption or any bluish exhaust, and the fact that you experience a return to decent performance practically rules out compression issues (bad rings --> oil in cylinder --> misfire or burned valve --> low compression on 6 --> misfire), because compression issues won't come and go.


My conclusion - while it may be worth following up on the misfire, it seems highly unlikely that the relatively low frequency of occurrence can be related to a semi-consistent loss of power (ie all summer). For your original problem, this misfire probably is just a wild goose

If you wanna chase it further there should be a service info out there similar to this one, I just didn't look hard for it

Cheers

 

[gmcman]

Capt,
Have you performed a compression test yet?

Compression test and also a few days of driving with that 44K can help alot. At least we will know if the misfire is from lack of compression and/or if there is sufficient carbon in the chamber that is pre-igniting the mixture causing a retard of the timing, thus resulting in poor performance.



Have you done the paper test on the tailpipe yet as well? Post# 112 as well as #99 has some tips. Please let me know your findings, and will aid in my and others' diagnostics.

 

[CaptainXL]

So that should be P0306 right? Any other codes associated with it (not sure they'll show up in the log)?

There should be a P0306 but weather or not that gets stored for any amount of misfires or if the PCM waits until a set amount (say 24000) misfires occurs...your guess is as good as mine. Either way, it's minimal and I don't think I have a real issue here. If nothing gets stored in the HISTORY I am satisfied nothing is wrong.

Capt,
Have you performed a compression test yet?

No, just haven't had time yet ferrying the family to Detroit over the past week. Still plan to.

Have you done the paper test on the tailpipe yet as well? Post# 112 as well as #99 has some tips. Please let me know your findings, and will aid in my and others' diagnostics.

Will do. In the past I did notice a strange warbling sound emanating from the tailpipe. I chalked it up to the way our exhaust is designed. I have never hear anything like that. When I put my ear next to the exhaust it sounded uneven or almost like hardly any exhaust was coming out. But I know that can't be the case because the backpressure tested perfect.

Here is my log from Torque. Notice many of the cylinders read 0 for misfires. Other than 6...a perfect record! Also according to Torque i get over 300HP which we know can't be right. Still trying to figure that out. My profile information including weight and such is correct.

 

[CaptainXL]

Did a compression test today. Got 120 psi on 1 thru 5 cylinders and 110 psi on 6.

According to Alldata my compression should be 150 psi minimum and 215 psi typical. So this looks like I have major problems.

 

[gmcman]

I just need to ask and hope I don't sound like I'm insulting your intelligence, the compresson tester....did it have an O-ring on the seat and did you use any type of extension tube on the end of the tester?

Those are real low figures which is why I ask, and seems too low and uniform for your miles.

Did the engine ever overheat that you know of...ie, at about 260F for any length of time?

I would let the 44K run it's course and run it up from 3500-6000 in 2nd a few times at WOT near the end of the tank, and note any debris from the exhaust.

This will at least remove the valves from the equation and HOPEFULLY you have some carbon under the seats.

 

[CaptainXL]

I just need to ask and hope I don't sound like I'm insulting your intelligence, the compresson tester....did it have an O-ring on the seat and did you use any type of extension tube on the end of the tester?

Hehe. Im not feeling too intelligent today anyway. Especially when the local AutoZone clerk tells me that he has rebuilt 4 of these engines and comenting that they are easy. I had to poke and prod him just to be sure.

Yes I did use the extension tube. It made it easier to thread the hose onto it. Why? Are you able to thread the hose directly into the spark plug well? And yes the o-rings were in good shape and sealed properly. I have only used a compression tester a few times but I think I did it right. I did however forget to add a couple tablespoons of 30 weight oil to see if the rings were worn. Darn. Might need to go back and rent it out again.

Those are real low figures which is why I ask, and seems too low and uniform for your miles.

Agreed. Engine runs fine and at times I get decent 0-60 times. Something doesn't seem right. I've been reading up on this stuff and there are other possible variants to consider including stretched or skipped timing chain. Hope its not that!

Did the engine ever overheat that you know of...ie, at about 260F for any length of time?

No, not that I know of. It had a failed thermostat from the previous owner. I am guessing it faile open.

I would let the 44K run it's course and run it up from 3500-6000 in 2nd a few times at WOT near the end of the tank, and note any debris from the exhaust.

I think its already working. I used the paper method of checking the exhaust and it comes out in a steady stream. It's blowing out a ton of carbon carried by the water vapor at idle.

This will at least remove the valves from the equation and HOPEFULLY you have some carbon under the seats.

I think I might need to do a leakdown test next just to be sure.

 

[gmcman]

Yes I did use the extension tube. It made it easier to thread the hose onto it. Why? Are you able to thread the hose directly into the spark plug well? And yes the o-rings were in good shape and sealed properly. I have only used a compression tester a few times but I think I did it right. I did however forget to add a couple tablespoons of 30 weight oil to see if the rings were worn. Darn. Might need to go back and rent it out again.

The extension tube will lower the compression, depending on the length it will be dramatic. The combustion chamber is only so big and the tube will add to the dimension thus lowering the pressure. The tester may have a chart to add a percentage when using the tube but not sure.

#6 will be a pain without the tube but just thread it down until it stops then snug it against the O-ring. You could compare the values without the tube on 1-4 and you will likely see they are uniform but at a higher value.

Also, how fast does the compression rise with each stroke (compression)? What does it hit on the first cycle?

Don't do the oil yet and try them dry. You can test dry first then add a few drops and see if it rises much higher but with the uniform values I think it may have been the tube.

 

[CaptainXL]

The extension tube will lower the compression, depending on the length it will be dramatic. The combustion chamber is only so big and the tube will add to the dimension thus lowering the pressure. The tester may have a chart to add a percentage when using the tube but not sure.

#6 will be a pain without the tube but just thread it down until it stops then snug it against the O-ring. You could compare the values without the tube on 1-4 and you will likely see they are uniform but at a higher value.

Also, how fast does the compression rise with each stroke (compression)? What does it hit on the first cycle?

Don't do the oil yet and try them dry. You can test dry first then add a few drops and see if it rises much higher but with the uniform values I think it may have been the tube.

The compression for each started at about 40 psi and took about 10 cranks to get to 120 psi. Some extension tubes have an o ring but the Great Kneck OEM one I used did not. The actron or equus has an o ring on the extension tube. Not sure if that makes any difference. Gonna try this again one more time and see if the rings or valves are the issue by using oil.

 

[gmcman]

10-15 Bumps on the starter isn't bad, that's prob 4-5 bumps per revolution.

Remember you get compression on every other stroke. your 40 could have been on mid- stroke.

Try it on a few without the extension tube.