I-6 Throttle body questions

[WarGawd]

Hey all -

Trying to keep this short and sweet so I won't delve into a lot of background.

Since the Fall I've been contending with intermittent SES & REP occurrences. When it first occurred in Sep, I happened to have my laptop and scanner in the vehicle because I was due for my Drive Clean test, and was wrestling with a (previously intermittent but suddenly persistent) P0455 Evap large leak.

While backing down a driveway, as I accelerated, the SES lit with REP. Several attempts to restart didn't clear the issue, so I copied the codes and cleared them and it restarted fine. Probably another two months went by without issue, and the next occurrence of REP was cleared up with a single restart. Same goes for the next few that seemingly began to happen more often as winter progressed, always associated with my trying to hit the gas too hard or too fast. Single restart always resolved it until tonight. Associated codes (for the times I captured them, but didn't every time) were P2101, P2176, P1516 and another that I cant find but was related to APP sensor range or circuit performance or something.

Over time while I was researching troubleshooting and forum posts, I started to get the feel that the ignition switch might be involved in many of these, and even if not, it's a cheap swap to eliminate one possible factor. I ordered one, haven't installed it yet.

Tonight, multiple restart attempts wouldn't resolve the problem. Limped home on REP (15km), plugged in the scanner and cleared the codes...but immediately on start the codes reset - this is primarily the P2176 Idle Position Not Learned. (FYI my scanner tells me P1516 is "manufacturer defined" LOL, so helpful)

Googled a bit more and recalled the 5V reference is common to the APP, TB and fan clutch. Disconnected the fan clutch harness connector and attempted restart, engine ran but still with REP and SES and associated rough idle. I have no known issues with my fan clutch operation, one of the lucky ones I guess).

In blowing snow and dim light underhood I tried to check for 5v reference on the harness connector and found one pin did have exactly 5.01V on it, just didn't have a pinout diagram handy to verify its the correct pin (IIRC its blue wire, 2nd pin in from unpopulated slot). Wouldn't mind a pointer to the TB connector pinout to see where to check its 5V reference.

Also disconnected the negative terminal on the battery to see if it would resolve the issue before attempting to clean the TB. While disconnecting the terminal, I observed ODD behavior including but not limited to engine cranking (key was off), and very loud steper motor or pump of some sort in engine bay area (didn't last long enough to pin it down). Upon reconnecting battery ~15 minutes later and attempting restart, SES and REP got thrown right away. Engine revs to ~2k rpm for a couple seconds (it's during this period that I believe the PCM is trying to command the TB stepper motor to position the butterfly plate to the correct position for achieving idle speed within tolerance around 600 rpm).

Next I removed and cleaned the throttle body. It was probably overdue (~2yrs since last) and was definitely dirty but not so much as to impinge of motion of the butterfly plate. It seemed to move freely, and in general was about as dirty as the last time it was cleaned, which is nowhere near as bad as many example posted on the forums.

I was about to reinstall the TB, but noticed that in a certain position, induced motion of the butterfly plate resulted in grinding noise from the stepper motor /sensor housing area. Inverted 180 degrees the noise goes away. Mild shaking of the TB sound like loose bits inside (http://gmtnation.com/forums/threads/throttle-body-grinding-anyone-had-this-issue-before.12112/) - I'm thinking I may have stripped a tooth before on the plastic gear wheel, possibly due to age/fatigue and perhaps the gear finally fell apart tonight. I don't recall this noise the last time I cleaned it, and likely would have enquired about it back then.

(So much for short and sweet, I can't ever manage!)

SO - now to the questions:

1) Has anybody else who's R&R'd their TB ever noticed noise from the stepper motor / sensor housing area and found the TB was working just fine? (IE maybe a little noise is "normal")

2) Where on the TB connector is it's 5V pin?

3) Is it a safe assumption that if the 5V is present on the connector(s) that it isn't being affected somewhere else ( IE I read about internal fan clutch short possibly pulling it low)

That's it for now. Add anything you think may be relevant
Thanx in advance

 

[Sparky]

1) Pretty sure mine had no rattle. It moved smoothly too.

3) No. It isn't being affected NOW, but, if you have chafed wires someplace it could be randomly affected elsewhere. Although, it could be affected by something inside the throttle body if that is acting up.

 

[littleblazer]

I actually cleaned the tb on the voy Friday and noted loose bits rattling around inside as well. Strangely enough after 90 miles at 75 mph approaching an off ramp the throttle suddenly bliped wide open on my father. I think it was the operator but he said his foot was off the gas. I was in the car and did notice it shoot up. Otherwise no issues there. Throttle blade seemed easier to open than I recall mine being. I would go out on a limb and say the loose bit probably shouldn't be loose and if you got 5v on 1 pin that's probably it. I believe @Mooseman has a link to the factory service manuals and there are diagrams in them.

 

[mrrsm]

@WarGawd ...

Even though this information is for an LS2… The OBDII Investigative Procedures and the Code Diagnostic Information at the very bottom of this page might prove helpful:

http://www.ls2.com/boggs/dtcs/DTC P1516_P2101_P2119_P2176.htm

 

[WarGawd]

Thanx guys -

I guess I'll take a chance on throwing it back in and see what happens...updates later

I should note that this is a spare PCM I used for the PCM4Less tune...I have the original...not sure if its easier to eliminate the PCM as a source of the issue by swapping in the old one or running the tests linked by @MRRSM...especially in this weather right now...I'll think on it , mean time I could do a better job inspecting for bad wire at the harness per another recently updated thread, now that it's actually daylight...

 

[Mooseman]

Hey, @WarGawd , how's my favourite rocket scientist?

You should just go over to Kenny U Pull and grab a throttle body. I think yours is borked. Maybe grab a gas pedal while you're at it. Should be cheap enough.

 

[WarGawd]

@Mooseman - Since I've now reinstalled the spotlessly clean TB with no change, I may consider that option, though transportation to and from Smiths Falls is a bit of a barrier at the moment.

For all following this, some updates -

Prior to reinstalling it I rotated the TB around and gently shook it while moving the plate, and found in one or two instances that the plate actually jammed briefly. At any point when the sensor/motor housing is more than ~10 degrees below the horizontal, the grind noise will not occur. When rotated such that the sensor/motor housing is ~10+ degrees above the normally horizontal axis of the plate, the noise is present. Shaking always results in loose material of some sort bouncing around inside.

I've further done a fairly thorough tug test on the harness at the TB connector and found all to be secure and robust and solid. Didn't yet try the same on the fan clutch connector

Since I have a brand new one handy and it's fairly easy, I'll swap in the new ignition switch next. I have other semi-vague indications of switch related problems, one of which just started last night - failure to crank turning the key, multiple attempts sometimes required. That plus last nights odd behavior of the starter cranking while simply disconnecting the B- terminal with the key off and the frequency of problems with this particular part.

I'll update when that's done and re-evaluate from there...at least its daylight and not quite so cold today

*Edit - as an afterthought I wanted to mention I checked battery voltages - when off it's 12.78, when running it's 15.16, alternator is about a year old, battery is about 2-1/2 y.o fairly high end AGM type that's never been discharged to any significant degree

 

[WarGawd]

Hey, @WarGawd , how's my favourite rocket scientist?

You should just go over to Kenny U Pull and grab a throttle body. I think yours is borked. Maybe grab a gas pedal while you're at it. Should be cheap enough.

Ok the new ignition switch is in and I managed to nail the gear position 1st time. On my newer switch there's a reference dot that does NOT coincide with the TWO reference dots marked on the old switch. For any future reader searching "ignition switch replacement" the correct alignment turns out to have gear tooth #3 positioned at TDC in the wheels rotation. This would coincide with one of the markings on the old switch, and would place the gap between teeth #2 & #3 in line with reference mark on the newer switch. I have pics I'll post in another thread later.

On the subject of Kenny U-pull, I'm leaning a little stronger in that direction @Mooseman --- have you seen anything on the lot lately?

On a related note if anyone has a moment to add any other vehicles they know to use the AC Delco 217-2296 (OEM PN 12568580) throttle body it'd broaden my search at the U-pull lot. Obviously I know the TB's and Ascenders and other variants of this platform, but I think they're used on the Canyon and Colorado among others.

I'd also like if anyone might put up a summary of the general sequence of events on startup as it pertains to the throttle body. The reason I ask is I have now noticed that it appears to cycle (or flutter to use other peoples words) when the key is initially switched to Run....the reason I noticed this today is that with the hood open and door slightly ajar I could hear the grindy noise of the throttle actuator motor in it's apparent attempt to adjust the throttle plate position even prior to attempting to Start. Hadn't ever noticed this before and unsure if it's normal or new behavior.

TIA

 

[WarGawd]

FYI Kenny U-Pull in Ottawa returns two Impalas and an '05 Envoy as potential matches on the lot now when I searched using my '05 XL as a reference model - guess any other compatible vehicles would have been identified (maybe?)

Further, Rock Auto cross reference says Hummer H3 as well as Grand Prix and Monte Carlos in addition to Impalas Canyons and Colorados

Off to work - will check back in around 11pm

 

[littleblazer]

Any engine in the atlas family works I believe. So the i5 in the hummer and Colorado/canyon and I guess the i4 in the impala?

 

[Mooseman]

Gatineau is showing another Envoy.

Here's the full cross reference for your year throttle body:

BUICK RAINIER 2004-2007
CHEVROLET COLORADO 2004-2007
CHEVROLET IMPALA 2006-2007
CHEVROLET MONTE CARLO 2006-2007
CHEVROLET TRAILBLAZER 2003-2007
GMC CANYON 2004-2007
GMC ENVOY 2003-2007
HUMMER H3 2006-2007
ISUZU ASCENDER 2003-2007
OLDSMOBILE BRAVADA 2003-2004
PONTIAC GRAND PRIX 2006-2007
SAAB 9-7X 2005-2007

 

[WarGawd]

Thanx @Mooseman I'll keep that one in mind if I have no luck in Ottawa - probably plan on heading in early tomorrow.

 

[Sparky]

The throttle body flutter at key turn is normal.

 

[WarGawd]

The throttle body flutter at key turn is normal.

Ok perfect thanks...now hearing the noise of it that I'm sure I'd have noticed before gives me some hope that there really is some mechanical failure inside and I've found the cause of the problem. Otherwise, I'm really starting to wonder what my next step would be if throttle body changeout doesn't fix it.

 

[Sparky]

Mine would do the flip-flip when keying the ignition, but never grind/snap/pop/grumble/whatever. It has a little mechanical sound to it from the gearing inside, but I wouldn't call it grinding.

 

[Mooseman]

Like I said, grab the pedal too. Never know.

 

[WarGawd]

Mine would do the flip-flip when keying the ignition, but never grind/snap/pop/grumble/whatever. It has a little mechanical sound to it from the gearing inside, but I wouldn't call it grinding.

Well as it turns out I snagged a throttle body off a 2005 XL and I knew as soon as I had it off the vehicle that my original had a serious problem. The salvaged one had no sign of the "rice grains rattling in a tin can" sound when I shook it.
It was filthy and I'm almost sure it had never been cleaned, although there was a minor nick in the sharp machined edge that I can't see having been there as a factory new part. I polished it clean and reinstalled it and it fired up right away with CEL and REP lights gone and settled in at a proper 600 rpm idle.

So I'm very happy to have the problem MOSTLY beat...more below.

Like I said, grab the pedal too. Never know.

I already texted this reply to Mooseman, but for other readers I was unable to use the pedal as mine are the adjustable type and the scrap vehicle was not.


FURTHER UPDATE: The original throttle body almost certainly had an internal mechanical failure. Either the plastic gear or some part of the sensor disintegrated inside the housing. I kept the old part to dismantle to see which it was and will post a few pics soon.

I thoroughly cleaned the salvaged unit to a nice shiny polished state and I had the battery disconnected the whole time. After driving it a while after initial startup, I noticed there was a slight roughness to the normally smoother idle, rpm occasionally dipping to 550ish. In gear idle at full stop exhibits the same characteristic. On take off, there is a slight momentary stumble around 800 rpm. Once I'm above 1k or 1100 rpm, around 20km/h or so, I can hammer the gas to the floor and get full power with no hesitation. This behavior seems consistent and repeatable.

As an experiment I drove around and found a few variously sloped hills where I could apply throttle without the vehicle moving. I find I get the stumble/hesitation/miss consistently between idle and around 900 rpm, even if i very slowly and smoothly apply power. Above that 1k mark, again as I said I can go smooth and steady or jam it and have no evidence of any problem.

Not quote sure what to make of this. I was careful around the coil packs that are near the lower two throttle body bolts, didn't dent or distort the heat sink blades so I'm unlikely to have damaged one, the connector and vacuum line and all the air intake hoses and clamps are back in place & secure and while I did swap the gasket because I had a warmer more pliant one in reserve, I cleaned the indent where it seats and it was in good shape with no cracks or nicks etc.

Gonna search a bit after I post this but if anyone has suggestions please post them.
Thanx again everyone - SOOO nice to have my truck back instead of a borrowed Honda Civic!!

 

[Mooseman]

I doubt it's a coil as you would get a CEL for a miss. But if you have a Bluetooth OBD adapter, wouldn't be a bad idea to check for misses. At the same time, check the O2 sensor readings and voltages to see if it's getting lazy.

Other than that, I'd just throw at you the questions about maintenance, plugs, air and fuel filters, etc. There's also the CPAS to check.

 

[WarGawd]

I doubt it's a coil as you would get a CEL for a miss. But if you have a Bluetooth OBD adapter, wouldn't be a bad idea to check for misses. At the same time, check the O2 sensor readings and voltages to see if it's getting lazy.

Other than that, I'd just throw at you the questions about maintenance, plugs, air and fuel filters, etc. There's also the CPAS to check.

I have a scanner - OBD Link SX - I can record some data and see if I can spot anything but honestly not really sure how to interpret a lot of it. It did throw a code last night after several ignition cycles, almost positive I'm going to find the P0455 that was outstanding prior to this.

Even given the above the vehicle ran smooth and had no hesitation or roughness at idle. Yes I was afraid to nail the gas because it always caused the REP inconvenience and I'd have to pull over to restart but there was never this issue.

My searches last night turned up relatively little. Since the throttle body is the biggest variable that has changed I'm inclined to focus there. Either something I did in the process isn't quite right, or I introduced some change. OR this TB has an actual issue that likely caused the same problem for the owner of the salvaged vehicle I got it from.

Plugs are the 41-103 changed about two years ago. IIRC the fuel filter is in the tank on these not meant to be changed for vehicle life (wouldn't there be MORE of an issue at higher rpm with filter restriction?). The air filter on this never seems to get very dirty so it has been a while since I actually checked it, but again I can't see how that would suddenly have an impact when none has been evident in the months prior to this.

I do know that some tests that would ordinarily throw a code don't get run if certain prerequisites aren't satisfied or if other codes are present. Maybe someone could verify for me that the presence of an existing or pending P0455 doesn't "block" the reporting of the P0300 & P030x series for misfires?

I'll go out with the scanner in a bit and check what's really there, record some real time data as well as pull off the airbox and check things out. Possibly even video the butterfly valve motion with key switched to Run.

Updates in a while

 

[littleblazer]

If you can log the throttle position and pedal position you can check for any inconsistencies. Should be a smooth acceleration curve. Punching it out and getting rep to me means some sensors aren't agreeing be it the throttle body or pedal. Try it and log what happens. They should be within 2% or something like that. I know on the v8s they are picky about pedal, throttle body and that throttle computer all matching. Chaning ome causes issues like random rep but I think these don't suffer that same fate. Unless you are staying that didn't happen then disregard that.

Evap codes shouldn't block misfire codes but lack of the right computer Will, at least for a specific cylinder did you say you had a loaner installed?

The evap if it's intermittent could be the canister failing. Check the lines for charcoal as I have a similar intermittent issue on our envoy.

I think I answered what you were asking? If I didn't sorry.

 

[WarGawd]

If you can log the throttle position and pedal position you can check for any inconsistencies. Should be a smooth acceleration curve. Punching it out and getting rep to me means some sensors aren't agreeing be it the throttle body or pedal.

So yes I now believe that's exactly what was going on here. The sensor in the housing had degraded to a point that on sudden or large throttle excursions there would be a mismatch between commanded and reported positions. The event the other night I'm almost certain was the final stage where the sensor disintegrated completely (the noisy bits shaking around inside). I will know for certain once I crack it open and inspect just to satisfy my own curiosity. If the sensor disintegrated completely as I suspect, it's a perfect explanation for the P2176 failure to learn idle position on startup.

Upon replacing the TB with a salvaged unit, the P2176 vanished instantly, and as a result the PCM didn't need to enforce REP, however I now have a low speed low throttle misfire that's not apparently severe enough to throw a code.

Evap codes shouldn't block misfire codes but lack of the right computer Will, at least for a specific cylinder did you say you had a loaner installed?

Not quite - I'm still in possession of my original PCM, but the one currently installed is the one I had tuned by PCM4LESS and which has been on the vehicle for 4 yrs. I was suggesting earlier that if we suspected the PCM was possibly being considered the root cause of the P2176, then rather than troubleshooting by performing the continuity and voltage checks prescribed in that diagnostic link, I could simply swap back to my original PCM. This is no longer necessary as I've determined there's a definite mechanical failure in the original TB that caused the issue. The PCM seems exonerated.

The evap if it's intermittent could be the canister failing. Check the lines for charcoal as I have a similar intermittent issue on our envoy.
I think I answered what you were asking? If I didn't sorry.

The Evap VENT valve is normally open. The Evap PURGE valve is normally closed, and is commanded open by the PCM under certain conditions in order to apply vacuum and test the Evap system. If the vacuum fails to be applied (purge valve doesn't open) or if it changes drastically immediately after (purge valve closed but vacuum fails to stay stable) the PCM declares a P0455 large leak. Nevertheless, it would be indicative of a leak in the evap system and in my mind not related to possible intake side vacuum leaks giving rise to the current misfire situation. Keep in mind P0455 has been present since at least last Sept and was intermittent for quite a bit longer before that, with zero evidence of this misfire/roughness/stumble on acceleration....I'm still leaning towards this misfire somehow being related to the new TB, whether it may somehow be defective too, or whether my multiple R&Rs changed something else yet to be determined

Still, I thank you for trying to contribute to getting this wrapped up

 

[WarGawd]

I doubt it's a coil as you would get a CEL for a miss. But if you have a Bluetooth OBD adapter, wouldn't be a bad idea to check for misses. At the same time, check the O2 sensor readings and voltages to see if it's getting lazy.

Other than that, I'd just throw at you the questions about maintenance, plugs, air and fuel filters, etc. There's also the CPAS to check.

OK so new info - I pulled the code and it is NOT the expected P0455. In fact in retrospect I think there is a prerequisite condition for running the Evap test that doesn't generally get met in the winter so the test won't even run. I forget now specifically which condition, but may be IAT being too low.

The code I pulled was in fact P0303 with another one pending. I'll go pull off the air box and look around. I KNEW I should have grabbed a couple coil packs off the Envoy I pulled the TB from while I was there, but with the time I spent salvaging a few other juicy parts, I felt like I was running out of time to get back home and get the TB cleaned and re-installed in daylight. Dammit!

I also logged a bunch of data from startup through warmup with a brief drive around and concluded with slowly applied throttle while in gear with brakes on up to about 2500 rpm. Again above 1k or so, no misfire or power loss.

Updates in a bit...

 

[Mooseman]

I KNEW I should have grabbed a couple coil packs off the Envoy

Isn't it always the case?

 

[WarGawd]

Isn't it always the case?

Must be some unwritten rule of life I haven't learned yet, Yep!

So I pulled off the airbox and had a good inspection of things. I took pics but I gather they have to be hosted elsewhere now? In summary all looked good to me. Pulled out the coil pack and the plug, pics would show evidence that the misfire hasn't gone on very long - plug is in good shape, no oil or moisture intrusion in plug well or connector. I did a tug test on the coil pack connector wires. SO since I can't spot any reason it should be behaving like this, I reinstalled the plug, swapped coil pack #2 with #3 and buttoned it back up.

I had cleared the P0303 codes prior to data logging, so I'll drive it for the evening and see if I can get it to throw another code. P0302 would be nice cuz that would point directly at the pack and I'd replace it. P0303 again would drive me back to some wiring or connector issue I think. Can't see how a vac leak would be cylinder specific (unless related to intake manifold bolts but that shouldn't have cropped up NOW on TB changeout).

I think that's all I can do for now...

 

[littleblazer]

The conditions for the evap test to run are air temp of 40 degrees, and coolant within 30 degrees of ambient you then need to move above 40 mph. That I know because I run it on the voy to clear the 0455 weekly. so if it's cold by you it won't run.

 

[Mooseman]

For pics, you can upload them here but they have to be reduced in size. Don't remember the limit but 100Kb is more than enough for on screen viewing.

 

[WarGawd]

For pics, you can upload them here but they have to be reduced in size. Don't remember the limit but 100Kb is more than enough for on screen viewing.

Hmm ok - I didn't spot the means yet but those now seem unnecessary. Maybe I'll check again when I attempt to upload pics of the pieces and damage inside the failed throttle body.

The PCM did throw a P0302 code at me while I drove it last night. Oddly the performance issue was significantly worse with the coil pack in this position, spanning a broader rpm range, with greater frequency of misfires. It had to run at 2400 rpm to get 100 km/h on the highway vs the normal 1800 or so.

Later that evening, I swapped the faulty coil from #2 to #1 in an attempt to gain a little more assurance I was really dealing with a faulty coil pack. I cleared the codes and hit the highway for a 2 hr drive. Engine ran MUCH better with the bad coil in this spot, though still some noticeable miss at idle/low speed, and frequent enough on the highway that it would kick down a gear a bit more often on uphill grades...on average though the rpm was right around normal at 1900 or so at 110 km/h and fuel mileage seemed on par with past performance on the same trip. In fact this time I could not even get it to throw the code after several ignition cycles.

This morning I went and grabbed a coil pack from a wrecker, plugged it in and problem is definitely gone. I will have to replace the coil one more time as the plastic lock portion of this one was broken off but for now electrically it functions fine.

As for what the cause of this coil pack fault/degradation is, I have a theory assuming it's anything other than purely coincidental:

Recall in the OP I had experienced weird electrical behavior on disconnecting and reconnecting the B- terminal. It happened again after I had swapped in the salvaged throttle body. In that instance I got a face full of headlight washer spray as I stood beside the vehicle reattaching the battery cable! It just all seems so odd...sparking and random circuit activation/completion...so my WAG is that somehow some voltage spike caused damage to the solid state coil pack.
I got no better theory, all I know is I was careful to avoid any physical impact or contact with them when I was accessing the TB bolts and I'm inclined to rule that possibility out.

As a conclusion to this thread, I'll post some pics of the actual failure mode of the TB when I crack it open this afternoon...after that I'm setting up to finally resolve my stupid ABS / hub issue.

 

[WarGawd]

Ok here is the final conclusion to this thread. Inside the throttle body, the motor drives a bi-level reduction gear to operate the throttle plate. As seen in the below pics, the main motor driven gear teeth are intact, but the reduction gear teeth that drive the throttle plate in opposition to the spring are all missing. Probably fatigued over 13 years and 290,000 km ending in total catastrophic failure!! (the gear wheel itself cracked during removal, but was intact when I 1st examined the inside):

 

[Sparky]

A little bit of superglue and you'd be fine

 

[Tiggerr]

O

A little bit of superglue and you'd be fine

JB WELD

 

[Snailblazin']

This was a great read and jam packed with excellent info. Thanks for being so thorough a troubleshooter!