Misfire / shuddering at low RPMs - 1995 Park Avenue 3.8 Series II

[chibuick]

Hi all, does anyone else have an issue with what feels like a misfire when driving at low RPMs and very little throttle? When driving down a perfectly straight smooth road I can feel a small shudder when at about 1100 RPMs and maybe 5% throttle and holding it steady. I feel it most when in 4th gear and torque converter has locked up for overdrive. I can watch the RPMs go up and down slightly during this, but this shudder/bucking goes away instantly when I give it more gas, or I let go of the gas entirely to coast.

This has been happening since I bought the car. I've replaced the throttle position sensor, coils, ignition control module, but has made no difference. I know it's not a transmission related since the trans was rebuilt last summer and this particular issue was unaffected.

Any help is appreciated!

 

[02LTD2.0]

Clean your MAF sensor.

 

[BuickGirlFromMars]

Hi all, does anyone else have an issue with what feels like a misfire when driving at low RPMs and very little throttle? When driving down a perfectly straight smooth road I can feel a small shudder when at about 1100 RPMs and maybe 5% throttle and holding it steady. I feel it most when in 4th gear and torque converter has locked up for overdrive. I can watch the RPMs go up and down slightly during this, but this shudder/bucking goes away instantly when I give it more gas, or I let go of the gas entirely to coast.

This has been happening since I bought the car. I've replaced the throttle position sensor, coils, ignition control module, but has made no difference. I know it's not a transmission related since the trans was rebuilt last summer and this particular issue was unaffected.

Any help is appreciated!

provide your vin number and i will get you the PROM chip code needed to alleviate this, this is called Chuggle.

note. the repair sets your lockup speed higher/delayed and other small things to reduce it

 

[chibuick]

Ok, I'll message you the VIN. I would love to learn more about this....is this the infamous torque converter clutch chuggle I've heard about (and laughed at the name)? Is it just the TCC rapidly engaging / disengaging based on what the computer's telling it? I have been complaining about lock up happening too quickly and easily on this 95. locks up at 46mph at 1,100 RPM.....lots of engine lugging. Sometimes I drive the car in 3rd gear just to avoid that. My 1996 with the gran touring suspension and the 3.06 final drive ratio on the trans doesn't lock up until about 55mph. Love it. Not sure if that's due to the different final drive ratio (instead of the 2.84) or something PROM/computer related that you mentioned.

Will also clean MAF. Thanks.

 

[BuickGirlFromMars]

Ok, I'll message you the VIN. I would love to learn more about this....is this the infamous torque converter clutch chuggle I've heard about (and laughed at the name)? Is it just the TCC rapidly engaging / disengaging based on what the computer's telling it? I have been complaining about lock up happening too quickly and easily on this 95. locks up at 46mph at 1,100 RPM.....lots of engine lugging. Sometimes I drive the car in 3rd gear just to avoid that. My 1996 with the gran touring suspension and the 3.06 final drive ratio on the trans doesn't lock up until about 55mph. Love it. Not sure if that's due to the different final drive ratio (instead of the 2.84) or something PROM/computer related that you mentioned.

Will also clean MAF. Thanks.

its not engaging and disengaging, its the firing pulses of the engine , under high load, and the transmissions direct connection to the tires
Its an exaggeration of everything about power delivery and mechanical tolerances , since the power isnt delivered smoothly constantly its present. it wasnt as noticeable in other vehicles or applications sometimes, its why they have always slipping TCC now , yours doesnt slip.

1996 with 3.08 may have been outside of the sensitivity range or it may have it stock/early owner brought it in, but its flashed on that pcm

 

[chibuick]

its not engaging and disengaging, its the firing pulses of the engine , under high load, and the transmissions direct connection to the tires
Its an exaggeration of everything about power delivery and mechanical tolerances , since the power isnt delivered smoothly constantly its present. it wasnt as noticeable in other vehicles or applications sometimes, its why they have always slipping TCC now , yours doesnt slip.

1996 with 3.08 may have been outside of the sensitivity range or it may have it stock/early owner brought it in, but its flashed on that pcm

Checked the MAF by the way. 4.3 g/s at idle and warmed. Didn’t clean it yet but figured that’s a normal value.

I’d imagine this doesn’t have much to do with final drive ratio as much as the shifting points and TCC lock up computer values. Can’t wait to get this 95 park Ave to not lock up till 55mph. Saw a few of your other posts here about it. Seems like upgrading the PROM (the memory chip in the PCM) fixes the issue based on the technical service bulletin from GM?

I hope this helps others if they see this and have the same issue.

 

[BuickGirlFromMars]

Checked the MAF by the way. 4.3 g/s at idle and warmed. Didn’t clean it yet but figured that’s a normal value.

I’d imagine this doesn’t have much to do with final drive ratio as much as the shifting points and TCC lock up computer values. Can’t wait to get this 95 park Ave to not lock up till 55mph. Saw a few of your other posts here about it. Seems like upgrading the PROM (the memory chip in the PCM) fixes the issue based on the technical service bulletin from GM?

I hope this helps others if they see this and have the same issue.

I cant use the website that checks for calibrations, the website just doesnt work. im trying to figure out a solution..
\

Try this!

Subject: Intermittent Chuggle or Fishbite on Light Acceleration or at Highway Speeds with No Diagnostic Trouble Codes (DTCs) (Replace Throttle Position (TPS) Sensor) Models: 1995-1999 Buick Riviera 1995-2004 Buick Regal 1995-2005 Buick LeSabre, Park Avenue 1997-2005 Buick Century 1995-2001 Chevrolet Lumina 1995-2002 Chevrolet Camaro 1995-2005 Chevrolet Monte Carlo 2000-2005 Chevrolet Impala 1995-1997 Oldsmobile Cutlass Supreme, Ninety Eight 1995-1999 Oldsmobile Eighty Eight 1998-2002 Oldsmobile Intrigue 1995-2002 Pontiac Firebird 1995-2003 Pontiac Grand Prix 1995-2005 Pontiac Bonneville with 3800 V6 Engine (VIN K -- RPO L36) ​ Condition​ Some customers may comment on an intermittent chuggle or fishbite on light acceleration or at steady-state highway speeds (typically 80-105 km/h [50-65 mph]) with no PCM DTCs set. This condition may lead the technician to suspect the TCC circuit or torque converter. Cause​ This condition may be caused by intermittent operation of the Throttle Position (TPS) Sensor. Correction​ In observed cases, the Tech 2® is not fast enough to consistently detect this condition during a snapshot. It is recommended to use a DVOM set to the min/max recording mode. Connect the DVOM at the TPS connector (positive lead to TPS feedback signal pin and negative lead to TPS ground pin). Duplicate this condition by driving the vehicle. If the voltage dropout (less than 0.45 v) is recorded on the DVOM, replace the TPS sensor and re-evaluate the vehicle before continuing with other driveability or transmission diagnosis. Parts Information​ [th] Part Number​ [/th] [th] Description​ [/th]​ [td] 24504798​

[td]

Sensor, Throttle Position (TPS)​

[/td]​

Warranty Information​

[/td]

 

[chibuick]

I cant use the website that checks for calibrations, the website just doesnt work. im trying to figure out a solution..
\

Try this!

​ Subject: Intermittent Chuggle or Fishbite on Light Acceleration or at Highway Speeds with No Diagnostic Trouble Codes (DTCs) (Replace Throttle Position (TPS) Sensor) Models: 1995-1999 Buick Riviera 1995-2004 Buick Regal 1995-2005 Buick LeSabre, Park Avenue 1997-2005 Buick Century 1995-2001 Chevrolet Lumina 1995-2002 Chevrolet Camaro 1995-2005 Chevrolet Monte Carlo 2000-2005 Chevrolet Impala 1995-1997 Oldsmobile Cutlass Supreme, Ninety Eight 1995-1999 Oldsmobile Eighty Eight 1998-2002 Oldsmobile Intrigue 1995-2002 Pontiac Firebird 1995-2003 Pontiac Grand Prix 1995-2005 Pontiac Bonneville with 3800 V6 Engine (VIN K -- RPO L36) Condition​ Some customers may comment on an intermittent chuggle or fishbite on light acceleration or at steady-state highway speeds (typically 80-105 km/h [50-65 mph]) with no PCM DTCs set. This condition may lead the technician to suspect the TCC circuit or torque converter. Cause​ This condition may be caused by intermittent operation of the Throttle Position (TPS) Sensor. Correction​ In observed cases, the Tech 2® is not fast enough to consistently detect this condition during a snapshot. It is recommended to use a DVOM set to the min/max recording mode. Connect the DVOM at the TPS connector (positive lead to TPS feedback signal pin and negative lead to TPS ground pin). Duplicate this condition by driving the vehicle. If the voltage dropout (less than 0.45 v) is recorded on the DVOM, replace the TPS sensor and re-evaluate the vehicle before continuing with other driveability or transmission diagnosis. Parts Information​ [th] Part Number [/th] [th] Description [/th] [td] 24504798​

[td]
Sensor, Throttle Position (TPS)

[/td]​

Warranty Information​

[/td]

Thanks, I replaced the TPS already with an GM genuine unit and it did not make a difference. I appreciate you checking the calibration website. Keep us posted!

 

[chibuick]

Looks like this is the TSB? https://www.tsbsearch.com/Buick/53-65-06A/138

Looks like on the last page of the PDF it has service prom, code, and ID for my application.