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

[wuffy68]

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:

I gave them a slight correction to the behaviour:

I have to say - I've been saying 'mid-throttle ... or .... half throttle' - THAT is actually not the case. At half throttle, the performance is actually smooth and impressive - it's more at the 25 to 30% throttle where I keep feeling that Kangaroo hop.

 

[wuffy68]

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

In my case - there are no trouble codes ... just speculating based on YOUR codes - have you tried cleaning or replacing the MAF? Maybe start with checking that it's connected (while in the area, check to make sure the air filter is clean, and properly installed). The IAT (Intake Air Temp sensor is usually integrated into the Mass Air Flow (MAF) sensor on late model GMs)

 

[abizzle]

In my case - there are no trouble codes ... just speculating based on YOUR codes - have you tried cleaning or replacing the MAF? Maybe start with checking that it's connected (while in the area, check to make sure the air filter is clean, and properly installed). The IAT (Intake Air Temp sensor is usually integrated into the Mass Air Flow (MAF) sensor on late model GMs)

I read something about the MAF sensor having multiple other sensors built-in. If I unplug the sensor, the check engine light comes on. It will turn off soon after reconnecting, but the codes persist. I've tried to manually clear them as well. I'm gonna run another scan at lunch and see if they're still there.

I'll just set this to the side and treat it as a separate issue. I don't wanna cloud our discussion with info that doesn't apply to both of us. Sorry about that.

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:

Yeah they're definitely the real deal. I continue to be impressed by the performance gains received from their tuning package. I can't remember... did you purchase the Trifecta Tune? Pretty sure we can say their tune has nothing to do with this issue. I would have expected the stutter to show up immediately following the ECM flash and that wasn't the case.

 

[wuffy68]

I read something about the MAF sensor having multiple other sensors built-in. If I unplug the sensor, the check engine light comes on. It will turn off soon after reconnecting, but the codes persist. I've tried to manually clear them as well. I'm gonna run another scan at lunch and see if they're still there.

I'll just set this to the side and treat it as a separate issue. I don't wanna cloud our discussion with info that doesn't apply to both of us. Sorry about that.


Yeah they're definitely the real deal. I continue to be impressed by the performance gains received from their tuning package. I can't remember... did you purchase the Trifecta Tune? Pretty sure we can say their tune has nothing to do with this issue. I would have expected the stutter to show up immediately following the ECM flash and that wasn't the case.

Nope - no tune on this one - wife's car, I don't drive it enough to justify the extra bump in power. I just contacted them to see if their tune could solve this occasionally reported issue by myself and other owners.

 

[wuffy68]

I've got one last silver bullet for this little gremlin ... way back, when I checked the air filter and the air filter box for disconnected hoses, connectors, 'n such, I cleaned the MAF with CRC MAF Cleaner - after which, the issue persisted, so I moved onto racing gas, plugs, CRC GDI cleaner, coils and VVT solenoids. I just ordered a new OEM MAF unit. I should have it tomorrow, hopefully this weekend I'll be able to tell if that was the problem all along. If so, I won't regret replacing the other components because I can tell, combined, they made the car run better at ~50K miles - they just didn't fix the part-throttle acceleration stumbling issue. What really chaps my hide is that two dealer techs couldn't 'feel' this issue while I was still under warranty. Another, at 20K miles, offered a $160 diagnostic to see if the valves needed walnut blasting (which apparently, wouldn't have been covered under warranty since they consider it a maintenance item). Note-to-self - always go on the test drive with your tech, since only you can reproduce your problem on-demand.

 

[wuffy68]

I've got one last silver bullet for this little gremlin ... way back, when I checked the air filter and the air filter box for disconnected hoses, connectors, 'n such, I cleaned the MAF with CRC MAF Cleaner - after which, the issue persisted, so I moved onto racing gas, plugs, CRC GDI cleaner, coils and VVT solenoids. I just ordered a new OEM MAF unit. I should have it tomorrow, hopefully this weekend I'll be able to tell if that was the problem all along. If so, I won't regret replacing the other components because I can tell, combined, they made the car run better at ~50K miles - they just didn't fix the part-throttle acceleration stumbling issue. What really chaps my hide is that two dealer techs couldn't 'feel' this issue while I was still under warranty. Another, at 20K miles, offered a $160 diagnostic to see if the valves needed walnut blasting (which apparently, wouldn't have been covered under warranty since they consider it a maintenance item). Note-to-self - always go on the test drive with your tech, since only you can reproduce your problem on-demand.

Put in the new OEM MAF (GM Genuine Parts ACDelco 23262344). Made in Japan - they've gone up in price recently. $71 was the cheapest OEM I could find online 🤔 I was optimistic at first, because the ECU had an adaptation period ... the CEL was on until I drove it for three short 'drive cycles'. The required adaptation period told me the new MAF was different enough for the ECU to recognise the swap. BUT in the end, no change in driving behaviour after driving it on a 40 mile round trip to the nearest town.

I did some further research on quirky torque converter lockup behaviour on these Aisin AWF8F45 8-speeds. I did a few light pulls using a "brake tap" method, where you keep your foot slightly on the brake during acceleration to prevent the torque converter from wanting to lock up. It seemed to stop having the shudder during these pulls (albeit it's not a very scientific method because it's hard to modulate the brake pedal while accelerating). A high volume transmission flush and filter replacement $$$ at the next oil service interval might do the trick. Fingers crossed.

 

[wuffy68]

Put in the new OEM MAF (GM Genuine Parts ACDelco 23262344). Made in Japan - they've gone up in price recently. $71 was the cheapest OEM I could find online 🤔 I was optimistic at first, because the ECU had an adaptation period ... the CEL was on until I drove it for three short 'drive cycles'. The required adaptation period told me the new MAF was different enough for the ECU to recognise the swap. BUT in the end, no change in driving behaviour after driving it on a 40 mile round trip to the nearest town.

I did some further research on quirky torque converter lockup behaviour on these Aisin AWF8F45 8-speeds. I did a few light pulls using a "brake tap" method, where you keep your foot slightly on the brake during acceleration to prevent the torque converter from wanting to lock up. It seemed to stop having the shudder during these pulls (albeit it's not a very scientific method because it's hard to modulate the brake pedal while accelerating). A high volume transmission flush and filter replacement $$$ at the next oil service interval might do the trick. Fingers crossed.

Dealer wanted too much for a WS-1 double flush - I took it to AAMCO ... they did it for a few hundred less (I did specify the GM fluid). They tested the transmission live data during acceleration and didn't find anything wrong. It feels like shifting is smoother now and allows more throttle input before I feel a light(er) shudder - they did detect misfires on cylinders 2 and 4?! This is after all the related parts (coils, plugs, MAF, VVT solenoids) were recently replaced 🤔 ... they suggested checking out the fuel injectors, or worst case ... cam shaft lobe wear (neither of which they work on). It's been doing this to one degree or another since 18K miles, so cam lobes, while possible, not as likely but never out of the question. Emission test-wise, it recently did a fast pass at Air Care Colorado (but that was simply a static inspection and code read). My next step is to check the gap on the ~new NGK 94374 LTR6IX Iridium IX ... some LTG performance threads indicate that the factory gap of .032" - .036" on these is NOT ideal (too wide) for LTG-x high-pressure turbo applications and recommend a range of .025"-.028". I'm going to set it to around .029"-.030" since the mechanic said .025" is way too small for stock boost levels. It could be multi-factorial (torque converter lockup/slip combined with misses from too wide a gap). More to come after this weekend.

 

[RETLAW]

Dealer wanted too much for a WS-1 double flush - I took it to AAMCO ... they did it for a few hundred less (I did specify the GM fluid). They tested the transmission live data during acceleration and didn't find anything wrong - they did however detect misfires on cylinders 2 and 4?! This is after all the related parts (coils, plugs, MAF, VVT solenoids) were recently replaced 🤔 ... they suggested checking out the fuel injectors, or worst case ... cam shaft lobe wear (neither of which they work on). It's been doing this to one degree or another since 18K miles, so cam lobes, while possible, not as likely but never out of the question. Emission test-wise, it recently did a fast pass at Air Care Colorado (but that was simply a static inspection and code read). My next step is to check the gap on the ~new NGK 94374 LTR6IX Iridium IX ... some threads indicate that the factory gap on these is not ideal (too wide) for LTG-x high-pressure turbo applications. More to come after this weekend.

This is wild. What an ordeal.

I changed out my plugs with the newest wonder metal version and gapped them down to .28. Didn't help my issue but mine was vvt salanoids. Seems like .28 is the go to for turbos. Even .26.

Im thinking about doing the trans fluid too. I have an aamco down town. Maybe ill give it a shot.

I doubt its the cams as well. Definitely could be injectors. Hell, its the only thing left really.

Man, I hope you get this sorted, so curious what the issue is.

 

[DrFaustus]

I'm in Colorado and take my TourX to Platinum Motorsport near Leetsdale and Monaco. Russian shop that specializes in European cars.

 

[wuffy68]

This is wild. What an ordeal.

I changed out my plugs with the newest wonder metal version and gapped them down to .28. Didn't help my issue but mine was vvt salanoids. Seems like .28 is the go to for turbos. Even .26.

Im thinking about doing the trans fluid too. I have an aamco down town. Maybe ill give it a shot.

I doubt its the cams as well. Definitely could be injectors. Hell, its the only thing left really.

Man, I hope you get this sorted, so curious what the issue is.

It's funny - my wife didn't really care - until we just bought a 2013 Volvo XC60 to replace my mother-in-law's failing 2002 S40. They have their own set of issues, but the XC60 drives really nice (turbo inline 6 helps). After driving that, NOW my wife gets what I've been talking about for years with the Buick. Yea, plug gap later today. Incidentally, had to wait nearly 3 weeks to get into AAMCO. They charged $520 for a diagnostic, double flush with WS-1 and an oil change. Dealer was over $800 (however dealers flush the trans using the coolant lines, so theirs would have been a more thorough flush, had I taken that path). I still love the TourX - it's a tank in the snow, cruises great, gets great mileage for something its size (it's just one of two in our small bedroom community outside of Denver (the other one being a white, Preferred model)).

 

[wuffy68]

I'm in Colorado and take my TourX to Platinum Motorsport near Leetsdale and Monaco. Russian shop that specializes in European cars.

Thanks for the referral ... it's on the opposite side of town, but maybe worth the trip if I get frustrated enough with it 😀 Or just let sleeping dogs lie until something actually breaks.

 

[wuffy68]

After changing the gap to .028" from the NGK factory .032", it's (mild shudder) still there between 2500 and 3000rpm (assuming 3rd gear) under moderate throttle acceleration, albeit slightly better. I lost my scan tool - will be picking up a new one next week, so I can try to see if there's still misfires being detected. Could it be sh** gas? Possibly now, since they closed our local Shell station - been putting in whatever's 91 octane is available, and just running Lucas fuel injector through every few tankfulls.

 

[wuffy68]

Well it took a month to get around to it. In between, we took the TourX on a 2200 mile round trip to SEMA in Las Vegas. It averaged 29.1mpg going over mountain passes, driving through desert two lanes to the Grand Canyon, and having to pass semi trucks that were themselves doing 85mph... It was an uneventful trip, the car cruised around great.

I did notice a new "symptom" along the way, since I normally don't drive the car (it's my wife's): accelerating from about 80mph to 95mph to get around lines of semis and motorhomes, I started noticing an occasional shudder. I first thought it was the snow tires (we didn't know if we would be facing blizzard conditions on the way back through Colorado's high country so we threw them on early this year, to be safe). The shudder appeared outside of Las Vegas when I suspected the heat combined with snow tires, but later it went away ... then in Arizona with cooler temperatures, I noticed it again. Going up from Silverthorne to the Eisenhower Tunnel in Colorado (it's a pretty hard climb that the TFL channel often uses for their towing tests), I had to take it 'easier' than I normally would to avoid the shudder. No check engine light or stored codes after coming back.

I finally checked it with Torque Pro today, and had it scan for misfires while I drove it through several moderate pulls from a dead stop. Some pulls felt perfect, other pulls I noticed the hesitation. I found misfires on all four cylinders, but mostly concentrated around cylinders #2 and #4. Attaching the screenshots from Torque taken during the shudder window. Taking it to local H&H Automotive next week ... is it carbon deposits, or a failing High Pressure Fuel Pump (HPFP), or ¯\_(ツ)_/¯

 

[abizzle]

Well it took a month to get around to it. In between, we took the TourX on a 2200 mile round trip to SEMA in Las Vegas. It averaged 29.1mpg going over mountain passes, driving through desert two lanes to the Grand Canyon, and having to pass semi trucks that were themselves doing 85mph... It was an uneventful trip, the car cruised around great.

I did notice a new "symptom" along the way, since I normally don't drive the car (it's my wife's): accelerating from about 80mph to 95mph to get around lines of semis and motorhomes, I started noticing an occasional shudder. I first thought it was the snow tires (we didn't know if we would be facing blizzard conditions on the way back through Colorado's high country so we threw them on early this year, to be safe). The shudder appeared outside of Las Vegas when I suspected the heat combined with snow tires, but later it went away ... then in Arizona with cooler temperatures, I noticed it again. Going up from Silverthorne to the Eisenhower Tunnel in Colorado (it's a pretty hard climb that the TFL channel often uses for their towing tests), I had to take it 'easier' than I normally would to avoid the shudder. No check engine light or stored codes after coming back.

I finally checked it with Torque Pro today, and had it scan for misfires while I drove it through several moderate pulls from a dead stop. Some pulls felt perfect, other pulls I noticed the hesitation. I found misfires on all four cylinders, but mostly concentrated around cylinders #2 and #4. Attaching the screenshots from Torque taken during the shudder window. Taking it to local H&H Automotive next week ... is it carbon deposits, or a failing High Pressure Fuel Pump (HPFP), or ¯\_(ツ)_/¯

Nice find! Can’t wait to hear what you find out.

I’ve got something to report as well, but I’m on my way out the door. Will post later today.

BTW, I’ll go ahead and setup my scan tool to log misfires and see if we can get some matching data.

 

[wuffy68]

Nice find! Can’t wait to hear what you find out.

I’ve got something to report as well, but I’m on my way out the door. Will post later today.

BTW, I’ll go ahead and setup my scan tool to log misfires and see if we can get some matching data.

Looks like I won't be able to get in until Dec. 1st... I'll have the GDI service done - walnut shell blasting (if it needs it), and have them check injectors and the HPFP operation.