I'm stuck, done a bunch with little improvement... please look

[Tuberattler]

Short story- 2002 Envoy I6- running rough misfiring-

Codes thrown- PO 304 & PO495 as read at Auto Zone. Misfire cylinder #4.

Definition: Cylinder misfire detected- cylinder number 4

Explanation: The power-train control module monitors the crankshaft speed and had detected a misfire condition.

Probable Cause: 1. Ignition system fault- spark plug(s), ignition coil. 2. Vacuum leak 3. Injector fault 4. high or low fuel pressure.

What I've done: Changed out plugs, ran better but still missing- Changed out Coil on #4- runs better now only missing every once in a while, but still basically UN-drivable and poor gas mileage.

Cleaned out Throttle body- reassembled and still rough running and missing-

Trip back to Auto Zone now it's misfiring on Cylinder #1

Been running injector cleaner in it as well. What next?

 

[djthumper]

the P0495 is your fan clutch - needs replacing most likely

How many miles are on the vehicle? What is your maintenance history like on the vehicle? How long has this been going on? What plugs did you use when you replaced them? Have you tried swapping coil 4 and 1 to see if it moves again?

 

[Tuberattler]

179,000 miles on vehicle,

This started all of a sudden and I've been trying to troubleshoot, not driving daily at this time.

Has had just basic oil changes & tranny service nothing else really.

I used Bosch Platinum II spark plugs- here's their ad copy- I didn't know about the AC plugs till I joined this forum.
Bosch Platinum 2 Spark Plug:

Smoother acceleration
Better gas mileage
Optimum engine performance
Uses surface air gap technology
Spark first travels over the surface of the insulator nose and then arcs across the air gap to a ground electrode for a longer spark
Does not increase the voltage requirement
More platinum in the center electrode
2 yttrium alloy ground electrodes help to reduce gap wear and oxidation, extending the service life of the spark plug

 

[HARDTRAILZ]

May be a dumb question, but have you unhooked the battery for awhile to let it reset after the changes you made?

 

[djthumper]

May be a dumb question, but have you unhooked the battery for awhile to let it reset after the changes you made?

Thanks, I knew I forgot to ask something else.

 

[Tuberattler]

Yes I've unhooked the battery, actually overnight. No real change.

 

[RayVoy]

I suspect you fixed the original mis-fire when you changed the coil on #4.


However, you now have a problem with #1, probably a "finger" problem (meaning, caused by your fingers).

You may have not properly seated the high voltage wire between the plug and the #1 coil.

Or, the #1 coil, or the #1 coil high voltage wire, was about to fail and you just sped up the process by moving it.

 

[fishguy1123]

Someone please chime in withe the delco plug # that is supposed to by used.. Thanks.

 

[Dad-O-Matic]

Someone please chime in withe the delco plug # that is supposed to by used.. Thanks.

41-103

 

[RedEnvoyDenali]

41-103

Is this the same plug used in 5.3 V8's?

 

[Dad-O-Matic]

Is this the same plug used in 5.3 V8's?

41-110

ACDelco Parts

 

[djthumper]

Dad's on top of those numbers.

 

[willn513]

I agree with the swapping coils idea. If the code moves, you know it's the coil. If not you can at least eliminate that,

 

[Numbnutz]

I had a similar issue last year....there were no more acdelcos where I went to buy my plugs...the guy swore by E4??. Plugs. Ran great for about ten minutes and then a huge misfire. I had lost two coils....tried it again and lost one of the coils I had just changed. A friend happened to be over and asked what plugs I used so I told him what happened....changed or the plugs again..bought another coil and problem fixed. We figured out the could by swapping then out with the others

 

[Chickenhawk]

Change to the 41-103 AC Delco plugs, get a new coil and be sure that all the coils are properly seated when you install them.

One of the downsides to coil-over-plug coils is that they are very susceptible to failure caused by misfires. If you use crap Bosch plugs or if they are not seated exactly right, they can fail in very short order.

I always love hearing about parts counter guys who "swear by" the product that they just happen to stock, instead of the product they don't stock!

 

[Tuberattler]

Here's where I am so far;

Miss on #4- changed plugs (Bosch I know I know)
After complete Plug change and coil pac on #4 I had miss on #1-
RE-seated coil on #1- that took care of that miss.

Ran injector cleaner expensive Cheveron. After all this it now runs rough and guzzles gas.

Sometimes it runs excellent- then a few minutes later it runs like crap.. What should I check now?

 

[The_Roadie]

CPAS and compression I'd check next.

 

[bore_pig]

Why skip the easy and obvious? If you are still having a problem, GO BUY THE RIGHT PLUGS! If there aren't already enough documented cases of plugs other than 41-103 Delcos causing problems, then what will it take? Are you trying to keep your new plugs just so you get your money out of them?

Step 1- Get the right plugs.
Step 2- Install them.
Step 3- Start vehicle.
Step 4- Swap coils around to find the bad one. (This step can be skipped in the event of smooth idling during Step 3.)

 

[Tuberattler]

Yesterday I drove it for 2 hours and it ran better than I've had it run in a long time... then as I'm cruising down the road for no reason at all it starts running real bad like the timing is off..

So my question would be this. How come it runs so good sometime and so bad others... btw it did this with the OLD PLUGS which WERE THE AC DELCO's

Question 2- If I get the right plugs and it still does this, which I'm sure it will - what would be my next step?

Compression probably isn't the issue if it runs so well about 1/2 the time now.

It feels to me like timing.

FYI- I do have some mechanical experience- I'm a certified on 2 cycle engines like in Ultrlight's etc. Although it was over 20 years ago I had my last mechanic's job- (I've sold Real Estate for 21 yrs) and I worked at an AC Delco Jobber and ran that warehouse for 3 yrs.. before I was 20. Oh yeah and I work on old tube amps (guitar) and have built several from scratch.. so I can usually figure things out pretty well.

 

[MichEnvoyGuy]

Why skip the easy and obvious? If you are still having a problem, GO BUY THE RIGHT PLUGS! If there aren't already enough documented cases of plugs other than 41-103 Delcos causing problems, then what will it take? Are you trying to keep your new plugs just so you get your money out of them?

Step 1- Get the right plugs.
Step 2- Install them.
Step 3- Start vehicle.
Step 4- Swap coils around to find the bad one. (This step can be skipped in the event of smooth idling during Step 3.)

+1,000,000,000,000

I too used plugs other than AC's at my 100k tune up. A week later, I had 3 misfires.

Took the plugs out (bosch?) put in the Delcos, and 50,000 miles later, not one misfire incidence or problem.

I realize you had the problem with the old plugs (delco) but you are risking more coil failures with the incorrect plugs in there - get them out.

Sounds like you have another issue going on too in the background. You dont have access to a handheld OBD2 scanner with live data by any chance, do you?

FWIW, a bad O2 sensor can make it run badly. No power, chug-chug-chug, and can seem intermittent at times.

 

[Chickenhawk]

You have now had some very experienced folks detail what you need to do. You needed one new coil because of misfires, and you will likely need another one. If they are not seated exactly right or one uses Bosch plugs, the coils can go bad in short order.

Honestly, the odds are against you. We have heard hundreds of stories from owners about misfires after changing to Bosch plugs; we have never heard of a single owner ever having timing problems. Ever.

So the ball's in your court.

As for the mileage issues, it is likely you drove the vehicle while it was misfiring (the Check Engine light would have been flashing) and your cat converter is now partially plugged. Once you get the misfire solved, you will need to do a simple and quick exhaust backpressure test done at a local shop or muffler shop.

Also, look at your coolant temperature gauge. When warm, the needle should point straight up or perhaps a tick to the right. If your needle is one or two ticks to the left of straight up, then it is time to replace the thermostat and/or the ECT sensor.

#1 - Fix the misfires. Get the proper plugs in there; make sure the coils are all seated properly and replace the one or two bad ones you now have.
#2 - Get your exhaust backpressure tested and let us know the readings at idle and at 2500 RPMs.
#3 - Tell us where your coolant temperature needle is sitting in the gauge.

Good luck and let us know how you are progressing. While it seems like insurmountable problems sometimes, almost everything that goes wrong with these vehicles is predictable and most are easy fixes with the help of the great folks in this forum.

 

[Tuberattler]

Ok OK Okkkkkkk!!!

I'm off to get NEW plugs.. I hope you guys can say I told you so

 

[ScarabEpic22]

I just noticed your down in the Tri Cities, Ive spent the last 4.5 years in Spokane but Im back in Seattle fulltime right now. Ill be passing through the Tri Cities on the night of the 10th if you want me to scan your truck with EFILive and see if there's another problem. It'll be late as Im leaving Portland at 8-9pm, and IIRC its about 3hr 45min drive so it'd be midnight at the earliest. But if you're still having problems and can spend 30mins with me taking a quick drive and letting me datalog your truck, I might be able to help you figure out whats wrong.

Let me know after the plugs what happens, the I6s are REALLY picky with plug choice, I ran Bosch Plat +4s in my 02 for ~30k and had a mis at idle plus lost 1-2mpg on them. Switched back to new AC Delcos, and instantly my starts were quicker (same battery), no miss at idle, and got my mileage back. Im a believer after that!

 

[Tuberattler]

Got plugs in hand now to install and see the wonder... I had AZ run their scan and now it shows random misses, so it probably is the plugs... arrrgghhhk... don't know if I can get them in this afternoon as I've got a showing this evening but if not then first thing in the morning before band practice.

Wanna see my band?... I'm the big one (country rock if anyone cares)


Greywolf - Home

BTW thanks for the offer of help, I may take you up on it if I can't get it resolved.

 

[Tuberattler]

Well I did it, I changed out the plugs again...(count to 10 for suspense) and everyone IS RIGHT!!! THANK YOU ALL!!

Well I still have some issues but now the truck runs pretty good. No major missing so far. Still runs a little rough and idles rough...hmmm

NOW I KNOW WHY there is a difference in these plugs.. here's some pix of what I found.

The Plugs I previously put in were Bosch Platinum II's.

View attachment 17760

 

[The_Roadie]

I'm sooooo glad I didn't leave you in the clutches of the noobs on the other site.

Let the PCM learn about the performance of the new plugs for a bit, and the idle may improve. If it's a 10 Hz vibration more than a varying idle, we have a fix for that. Can you describe the roughness with more precision?

 

[Wooluf1952]

Looking at pix 1 and 3, the gap seems to be double on the Bosch compaired to the AC Delco.

 

[plaen]

Interesting question to any one who used Bosch plugs. Has anyone tried returning the plugs to Bosch under their performance guarantee for a refund?

 

[Tuberattler]

On the rough running... it still has a misfire of some kind although much, much, much, much smoother than with the Bosch plugs.

Seems to run the best for the first 30-40 minutes then gets a little rougher as I drive. And pulsates at full stop or should I say as I come to a stop then smooths a bit when I'm fully stationary.

I want to give a shout out and a big thanks to everyone. Thanks to The Roadie for giving me the right detour over here and Chickenhawk for a little stern ass chewin' to get me to the parts store for round #2 with the right plugs... and of course all who suggested this course of action and a thanks to ScarabEpic22 for the kind offer of help which I may still take him up on.

On takin' the Bosch's back, I won't as I purchased them without doing the research. When I went to AZ it says right on their spark plug directory for our vehicle that "this vehicle came with Iridium Plugs" right above the various brand recommendations for the sales clerk. Although now that I think about it I bought them at Wal-mart and there was no such warning..hmmm... I'll have to think about it, I only had them in for about a week. Thought about putting them up on CL for a couple of bucks for cars that may be able to successfully use them.. what do you think?

Now to take wifey for a spin.... Ohh crap.. I bet you guys thought this was my rig... well my wife likes it, how should I say it.. more? No I like it more but a she gets as the daily and we use it when we're together.

 

[RayVoy]

Wal-mart will take those back, they have a satisfaction policy, take the receipt for the 2nd set with you, to show that you had to use the other manufacturer.

 

[The_Roadie]

Does the roughness change or get smoother if you're in NEUTRAL instead of DRIVE when stopped?

 

[91RS]

On the rough running... it still has a misfire of some kind although much, much, much, much smoother than with the Bosch plugs.

Seems to run the best for the first 30-40 minutes then gets a little rougher as I drive. And pulsates at full stop or should I say as I come to a stop then smooths a bit when I'm fully stationary.

I want to give a shout out and a big thanks to everyone. Thanks to The Roadie for giving me the right detour over here and Chickenhawk for a little stern ass chewin' to get me to the parts store for round #2 with the right plugs... and of course all who suggested this course of action and a thanks to ScarabEpic22 for the kind offer of help which I may still take him up on.

On takin' the Bosch's back, I won't as I purchased them without doing the research. When I went to AZ it says right on their spark plug directory for our vehicle that "this vehicle came with Iridium Plugs" right above the various brand recommendations for the sales clerk. Although now that I think about it I bought them at Wal-mart and there was no such warning..hmmm... I'll have to think about it, I only had them in for about a week. Thought about putting them up on CL for a couple of bucks for cars that may be able to successfully use them.. what do you think?

Now to take wifey for a spin.... Ohh crap.. I bet you guys thought this was my rig... well my wife likes it, how should I say it.. more? No I like it more but a she gets as the daily and we use it when we're together.

Does it vibrate at idle in gear? With the mileage you have you could need motor mounts if that is the case. If its still misfiring, your check engine light will come back on.

 

[Tuberattler]

Does the roughness change or get smoother if you're in NEUTRAL instead of DRIVE when stopped?

I'll take it for a test right now and get back to you with this one in a bit. Now I will tell you it's getting better all the time but out on the freeway earlier today I was going 70 and it started acting up running like either the fuel mix is off or the timing is retarded.. it did this for about 1/2 mile two or three times on a 30 mile round trip and it sometimes idles pretty good but others it's really fairly rough.

I'll be back after my showing and report.

HERE'S MY REPORT. No difference when I go into neutral or in drive it still vibrates and is loppy.. it's kinda like a miss but more of a lopping not a smooth idle.

 

[Tuberattler]

So based on what I've done and reported so far what would be my next logical step towards getting my rig running like it should.

I'm still experiencing poor running conditions and poor gas mileage.

 

[Chickenhawk]

You still have at least one bad coil. As it is idling, pull the connector on each coil in turn. The one that doesn't change the idle is likely the bad one.

After that, go back to page one and work through the other advice, specifically, get your exhaust backpressure tested and let us know where your coolant temperature gauge is pointed when warm. (Better yet, take a picture of it and post it.)

 

[Tuberattler]

You still have at least one bad coil. As it is idling, pull the connector on each coil in turn. The one that doesn't change the idle is likely the bad one.

After that, go back to page one and work through the other advice, specifically, get your exhaust backpressure tested and let us know where your coolant temperature gauge is pointed when warm. (Better yet, take a picture of it and post it.)

Ok, the coil test I can do, should I do this while the engine is running or turn off between dis-connecting the coil connector?

My temp it just a slight bit to the right of straight up.

Tell me a bit more about this back pressure thing as I've never done this one and am a ignorant on what it entails.