Feels like a misfire (coil packs?) - no fault codes detected

[wuffy68]

Sorry all - I thought I submitted an update but I must not have pressed the Post button... incidentally I had another more pressing issue to deal with on this vehicle ... see #post-75837
After replacing the plugs (above) and running the CGI intake cleaner through the system, I put in four new ACDelco GM Original Equipment 12654078 Ignition Coils. Is it better? Well ... the car runs stronger now, but the mild stutter during ~mid-throttle acceleration is still there. I'm inclined to think it's the "slip" reported by individuals who own vehicles with the Aisin AF50-8 transmission (and its variants). Next step is to have the transmission flushed and filter replaced during the next oil change. Either it's just a known quirk of the transmission -OR- the initial lessee (first 18K miles) hammered the car enough to accelerate fluid breakdown and start clogging the filter. I had a 2004 A6 2.7T lease return once - the mechanic who flushed the fluid at 60K miles said he's never seen one with such hard use (metal and fluid discoloration). There were tell-tale signs of the personality of the first owner/lessee that were hard to miss once we started cleaning the vehicle - they must have rodded the thing from every stoplight (those biturbo cars were faster than a 2004 Corvette in the first 60 feet). Anyway, more updates coming in the fall.

 

[wuffy68]

Shot in the dark but have you tried disconnecting the battery for a while to erase any “learning” the ecu may have stored?

Yes - recently while I was replacing the shifter console - I had it unplugged for nearly a week. Unfortunately - no difference.

 

[wuffy68]

Last night, I found it's getting worse. Going up a mild grade, starting from a stop with three people in the car, under moderate acceleration, it jerked about three times - assuming it was in 3rd gear at the time (around 35-40mph). I'm kinda at the point where I wish "something" would either throw a code or fail already 😅 so I can bite the bullet.

 

[RETLAW]

Last night, I found it's getting worse. Going up a mild grade, starting from a stop with three people in the car, under moderate acceleration, it jerked about three times - assuming it was in 3rd gear at the time (around 35-40mph). I'm kinda at the point where I wish "something" would would either throw a code or fail already 😅 so I can bite the bullet.

Did you change the oil control solenoids that control the cam timing? I dont remember.

 

[wuffy68]

Last night, I found it's getting worse. Going up a mild grade, starting from a stop with three people in the car, under moderate acceleration, it jerked about three times - assuming it was in 3rd gear at the time (around 35-40mph). I'm kinda at the point where I wish "something" would would either throw a code or fail already 😅 so I can bite the bullet.

Did you change the oil control solenoids that control the cam timing? I dont remember.

Not yet ... my understanding is that you can find out there's a problem with those starting with how freely (or not freely) the engine revs from idle (assuming either with traction control off or with the hood popped). Will try this later today. You may be onto something - you or someone else mentioned this earlier in the thread. Thanks!

 

[RETLAW]

Not yet ... my understanding is that you can find out there's a problem with those starting with how freely (or not freely) the engine revs from idle (assuming either with traction control off or with the hood popped). Will try this later today. You may be onto something - you or someone else mentioned this earlier in the thread. Thanks!

Well, in my case it ran fine at idle, but would start to kinda fumble around at 3500, then completely fall off the cam at 4500. Felt like power just flattened after 4500. I changed both intake and exhaust sides and it fixed the issue. I have read that it can feel like a miss fire in some cases depending on how the salanoids fail.
IDK, you could also close up the gap on the plug to like .26-28 area. Really weird situation you have going on! Possible injector failure?? Good luck!

 

[wuffy68]

Well, in my case it ran fine at idle, but would start to kinda fumble around at 3500, then completely fall off the cam at 4500. Felt like power just flattened after 4500. I changed both intake and exhaust sides and it fixed the issue. I have read that it can feel like a miss fire in some cases depending on how the salanoids fail.
IDK, you could also close up the gap on the plug to like .26-28 area. Really weird situation you have going on! Possible injector failure?? Good luck!

Thanks - yea, it idles smooth enough - it only shows up mid-throttle/mid-rpms. I went ahead and ordered the latest recommended ACDelco part numbers 12662736 (Intake) and 12662737 (Exhaust) solenoids which have better corrosion-resistant coatings (albeit they may have already made it into the TourX since they first appeared in the GM parts catalogs between 2014-2017) ... I read IF these engines are driven on just lots of short trips without being fully warmed up (might have been the case with the first owner/lessee, IDK), the solenoids can accumulate varnish quickly, and not work smoothly even with as little as 20K miles on the clock. Will know for sure by next Saturday.

 

[abizzle]

Thanks - yea, it idles smooth enough - it only shows up mid-throttle/mid-rpms. I went ahead and ordered the latest recommended ACDelco part numbers 12662736 (Intake) and 12662737 (Exhaust) solenoids which have better corrosion-resistant coatings (albeit they may have already made it into the TourX since they first appeared in the GM parts catalogs between 2014-2017) ... I read IF these engines are driven on just lots of short trips without being fully warmed up (might have been the case with the first owner/lessee, IDK), the solenoids can accumulate varnish quickly, and not work smoothly even with as little as 20K miles on the clock. Will know for sure by next Saturday.

It's next Saturday. LOL! I was checking back to see what happened. I sure hope the solenoids fixes it!

 

[wuffy68]

Thanks - yea, it idles smooth enough - it only shows up mid-throttle/mid-rpms. I went ahead and ordered the latest recommended ACDelco part numbers 12662736 (Intake) and 12662737 (Exhaust) solenoids which have better corrosion-resistant coatings (albeit they may have already made it into the TourX since they first appeared in the GM parts catalogs between 2014-2017) ... I read IF these engines are driven on just lots of short trips without being fully warmed up (might have been the case with the first owner/lessee, IDK), the solenoids can accumulate varnish quickly, and not work smoothly even with as little as 20K miles on the clock. Will know for sure by next Saturday.

So after replacing the VVT solenoids, again, it seems marginally better by a notch - haven't experienced any explicit 'jerks' during mid throttle/rpm acceleration (yet), however; there's still a 'bouncy' shudder in there - even if I manually lock it into 3rd gear, running 91 octane with a small bottle of octane boost at 5300ft of altitude. Maybe it's just how they are - they shift around the same time the VVT kicks which causes some confusion between the TCM and ECU. When I get the oil changed next month, I'm going to test drive and compare this to the 2025 Envision (still the same LTG engine - but with the GM 9 speed transmission).

 

[abizzle]

So after replacing the VVT solenoids, again, it seems marginally better by a notch - haven't experienced any explicit 'jerks' during mid throttle/rpm acceleration (yet), however; there's still a 'bouncy' shudder in there - even if I manually lock it into 3rd gear, running 91 octane with a small bottle of octane boost at 5300ft of altitude. Maybe it's just how they are - they shift around the same time the VVT kicks which causes some confusion between the TCM and ECU. When I get the oil changed next month, I'm going to test drive and compare this to the 2025 Envision (still the same LTG engine - but with the GM 9 speed transmission).

You think this is something that could be addressed via programming? Maybe the guys at Trifecta could look into it?

 

[wuffy68]

You think this is something that could be addressed via programming? Maybe the guys at Trifecta could look into it?

Thanks - I emailed them - we'll see.

 

[RETLAW]

So after replacing the VVT solenoids, again, it seems marginally better by a notch - haven't experienced any explicit 'jerks' during mid throttle/rpm acceleration (yet), however; there's still a 'bouncy' shudder in there - even if I manually lock it into 3rd gear, running 91 octane with a small bottle of octane boost at 5300ft of altitude. Maybe it's just how they are - they shift around the same time the VVT kicks which causes some confusion between the TCM and ECU. When I get the oil changed next month, I'm going to test drive and compare this to the 2025 Envision (still the same LTG engine - but with the GM

Thanks - I emailed them - we'll see.

Was really hoping the solenoids would help. So you've eliminated coils, plugs, cam timing. Don't these engines limit torque through 3rd gear to help the trans survive? Wonder if that is what your feeling. Wish we could be more help with your situation. Trifecta should be able to data log some driving, hopefully gets this resolved.

 

[wuffy68]

Was really hoping the solenoids would help. So you've eliminated coils, plugs, cam timing. Don't these engines limit torque through 3rd gear to help the trans survive? Wonder if that is what your feeling. Wish we could be more help with your situation. Trifecta should be able to data log some driving, hopefully gets this resolved.

It runs well enough - with a caveat you feel like you're driving a science experiment. Full throttle pulls feel "good" ... but everyday driving feel, or 'pleasure' is kind of taken out of the equation with this one so far. Can't expect miracles out of a 2.0L i4 regardless - it's doing a LOT ... and unfortunately, our previous car was an Audi 2.7T S-line which delivered it's power more smoothly (there I still complained because I always compared it to how our '97 BMW 740i 4.0L V8 used to feel - even though the 2.7T was faster at this altitude) 🙂. Before anyone pokes fun at this downward trajectory in luxury, next I'll be complaining about the driving dynamics of a rental return Hyundai Venue 😀

 

[bollox74]

random chime in here - do you have the stock air intake? Is the filter dirty? Is an O2 sensor bad maybe?

Spark, fuel, air.

 

[abizzle]

random chime in here - do you have the stock air intake? Is the filter dirty? Is an O2 sensor bad maybe?

Spark, fuel, air.

I am also chasing the same problem. I know I've changed my filter and replaced plugs with properly gapped OEM. I suppose I could adjust the gap to 0.26-0.28, as mentioned by @RETLAW.

It's a very annoying problem and it hasn't always been there. It's bad enough in "Factory" mode, but when I enable "Sport" mode the problem is more pronounced. It kinda puts a damper on the Trifecta Tune performance gains.

 

[RETLAW]

Wuffy mentioned something im trying to look into. Something about the Aisin 8 spds are known to not have a smooth power delivery? Im not having much luck finding info about these transmission, could anyone elaborate on what hes talking about or maybe point me in the right direction. I really dont luke the 8 spd in my car. Even with the trifecta tune its a turd and kinda surges a bit under full throttle.

 

[abizzle]

Wuffy mentioned something im trying to look into. Something about the Aisin 8 spds are known to not have a smooth power delivery? Im not having much luck finding info about these transmission, could anyone elaborate on what hes talking about or maybe point me in the right direction. I really dont luke the 8 spd in my car. Even with the trifecta tune its a turd and kinda surges a bit under full throttle.

I can't give you any specific data and I'm not a transmission guy, but Wuffy and I are having the same experience. I could describe, in detail, what it feels like to drive if you think it would help.

I'll also mention this because I suppose it could be related in some way. I have the following persistent trouble codes:

P0113 - Intake air temperature sensor - high input
P2227 - Barometric pressure sensor - range/performance problem
P2229 - Barometric pressure sensor - circuit high
P0097 - Intake air temperature sensor 2 - circuit low input; Intake air temperature sensor 2 circuit low voltage

 

[RETLAW]

I can't give you any specific data and I'm not a transmission guy, but Wuffy and I are having the same experience. I could describe, in detail, what it feels like to drive if you think it would help.

Yea, couldn't hurt. This thread is getting a bit lengthy and hard to remember everything we have already covered. I guess i should reread the whole thing lol.

 

[wuffy68]

random chime in here - do you have the stock air intake? Is the filter dirty? Is an O2 sensor bad maybe?

Spark, fuel, air.

Thanks, all stock AFAIK ... No O2 codes ... filter replaced 10,000 miles ago (still looks clean-ish)... the problem was there before replacing the filter.

 

[wuffy68]

Thanks - I emailed them - we'll see.

Here is Trifecta's very measured response to the issue ... these guys do sound like the real deal, but they really can't help until other things get resolved: