98 Buick PA - 3.8L Series II - Driveablility Issue

I have been trying to troubleshoot an issue with my '98 Buick Park Avenue with a 3800 Series II (non-supercharged) for the past 3 months...and need some more ideas. It has around 80K miles on it.

Whenever the car is up to operating temperature (160 degs or higher) it has a tendancy to stumble, more like fall no it's face, when accelerating from a stop. I basically have to feather the gas to get it up to speed...or stomp on it. I say tendancy...because the issue is intermittent. Around 50 percent of the time.

It doesn't have this issue when it is cold...actually runs like banshee until the computer kicks in.

The puter hasn't stored a code (of course that would be too easy). I have done my homework...both on this site and others trying to come up with a solution. So, over the past 3 months, I've loaded my "Parts Cannon" and blasted away. Here is what I believe is a complete list of components that I have replaced to date. I have placed them in chronological order:


MAF (Mass Air Flow Sensor) <It had a slight film on it from my K&N Filter -which I replaced with a paper one>
TPS (Throttle Position Sensor)
Spark Plugs, wires, & fuel filter
All 3 Coils
MAP (Manifold Atmospheric Pressure) Sensor <Replaced the PCV at the same time>
Both O2 Sensors (Front and Rear)
Fuel Pressure Regulator
IAT (Intake Air Temperature) Sensor <thought maybe it was ambient temperature related>
Crank Sensor

I replaced most of the sensors above due to my research finding that possibly some "could" be out of range without throwing a code.
I removed the EGR Vavle...to make sure it was moving freely. I've been brainstorming continuously...trying to come up with a solution.

Thought about the Catalytic Converter being plugged...then read about the notorious upper intake leaking some coolant into the exhaust and wiping the converter out. The EGR actually doesn't pass through the intake on this one...it is plummed remotely (sort of).

I am so fustrated at this point...HELP!

welcome to AF. Did you replace the MAF, if so some remans can be worse the the original one. Second is the fuel pressure consistantly up to par? Have you done a full scan to look at fuel trims, misfire counts and general sensor inputs, especially of course when the condition occurs. These are all basic diagnostic steps.

Haven't checked fuel pressure as of yet. The pump however is around 4-5 months old. Forgot to mention another item I replaced...the crank sensor. I just checked the injector pulse...at idle it's 3.3-4.0. During quick acceleration 7-8...with higher peaks. No codes active or stored...No misfires. Do you think I have lazy injectors???? Is the injector pulse recorded by the ODBII an average?

It is only what is commanded by the pcm, the injector pulse width is not live data on a regular scanner.. The fuel trims would show added numbers if the injectors were clogged/lazy. as this would cause a lean condition.

It is only what is commanded by the pcm, the injector pulse width is not live data on a regular scanner.. The fuel trims would show added numbers if the injectors were clogged/lazy. as this would cause a lean condition.
I have my brothers Matco pro scan plus hooked up...and driving. it says typical value is 1.5-3.5 msec....at idle mine is 4.0...at 69 mph on a flat road is 7.5.....on a grade 12.0 msec.

I have my brothers Matco pro scan plus hooked up...and driving. it says typical value is 1.5-3.5 msec....at idle mine is 4.0...at 69 mph on a flat road is 7.5.....on a grade 12.0 msec.

OK...did everyone hear that LOUD POP a few minutes ago. It was me getting my head out of my rear end!!!

I now understand that Fuel Injector Pulse Width is nothing more than the duration the injector it allowing fuel to be pumped. I guess I am reaching for ideas...and was hopeful that I found the culprit.

I have been trying to narrow this condition down. It seems the hesitation happens around 90% of the time when: 1) The engine is at the highest operating temperature, 185-195. 2) The outside temperature is above 85 deg. 3) The IAC reading is above 100.

It seems to be a complete hesitation of the engine...can't really say it is only one or two cylinders...and the analyzer didn't identify any missfires.

While you have the scanner hooked up, drive the car for awhile and watch each sensor reading to see if they are in spec. I would pay particular attention to the MAF, MAP & TPS readings @ idle and during acceleration. In addition, do a few "freeze frame" & data record scans and write down the readings, or do a printout. What is the LTFT & STFT @ idle?

I noticed that you have not replaced the ignition control module. Sometimes when the ICM begins to fail internally it tends to get flaky when hot. Give us some scanner readings if you can, under varying conditions. I.e. - hot, cold, idle & under light acceleration. BTW, fuel pressure check is a must. It should be around 44-48 @ idle and when you accelerate quickly, it should drop 4-8 psig.

While you have the scanner hooked up, drive the car for awhile and watch each sensor reading to see if they are in spec. I would pay particular attention to the MAF, MAP & TPS readings @ idle and during acceleration. In addition, do a few "freeze frame" & data record scans and write down the readings, or do a printout. What is the LTFT & STFT @ idle?

I noticed that you have not replaced the ignition control module. Sometimes when the ICM begins to fail internally it tends to get flaky when hot. Give us some scanner readings if you can, under varying conditions. I.e. - hot, cold, idle & under light acceleration. BTW, fuel pressure check is a must. It should be around 44-48 @ idle and when you accelerate quickly, it should drop 4-8 psig.

Yes...all the sensors are within spec. I plan to check the fuel pressure tomorrow after work. Is there anyway to check the ICM? If it had a voltage or something that would show up on the monitor...I have already checked it. Is it possible to bench test the ICM?

Also...do you know if the injectors would wig out when they get hot?

You can take the ICM to AutoZone and they can load test it for you. Ask them to test it several times in rapid succession for best results.

Also...do you know if the injectors would wig out when they get hot?
Injector timing is controlled by a signal from the cam sensor, which is passed through the ICM, and on to the PCM. If that signal is interrupted in anyway, yes the injectors could “wig out”!

In addition, be sure to check all the wiring from the CKPS, CPS, and the terminal connecting to the ICM. Also, check all the wiring from the ICM going to the PCM. A common failure area is, where the wires route over the top of water pump and under the alternator.

You can take the ICM to AutoZone and they can load test it for you. Ask them to test it several times in rapid succession for best results.

Injector timing is controlled by a signal from the cam sensor, which is passed through the ICM, and on to the PCM. If that signal is interrupted in anyway, yes the injectors could “wig out”!

In addition, be sure to check all the wiring from the CKPS, CPS, and the terminal connecting to the ICM. In addition, check all the wiring from the ICM going to the PCM. A common failure area is where the wires route over the top of water pump and under the alternator.

Thank you so much for the advice. I am removing the ICM tonight to take it into O'Reillys tomorrow for bench testing. If it is heat related...I will doubt that this test will result in any findings...but thought I would try anyway. I will trace the wiring like you mentioned...during its removal. Thanks again for your help.

Thank you so much for the advice. I am removing the ICM tonight to take it into O'Reillys tomorrow for bench testing. If it is heat related...I will doubt that this test will result in any findings...but thought I would try anyway. I will trace the wiring like you mentioned...during its removal. Thanks again for your help.

The ICM is mounted flat on an aluminum
bracket...the 6 coil retaining screws sandwich the ICM
between the coils and that bracket. I pulled the ICM off
for a bench test...and found the procedure called to ground
the ICM at the aluminum heat sink plate on the bottom. The
ICM tested fine. However I did notice oxidation on this
heat sink...and on the bracket. It pulls ground between
those two items when it is mounted. I sanded the sink and
the bracket, smeared a film of dielectric grease between
them, this should help the ground situation. Now I just did
this last night, so no long term verification. But after a
test drive...the hesitation was gone. I just hope with
higher ambient temperature during the day...it stays that
way.

If needed...I am going to check the fuel pressure next. I will keep you all updated.

The ICM is mounted flat on an aluminum
bracket...the 6 coil retaining screws sandwich the ICM
between the coils and that bracket. I pulled the ICM off
for a bench test...and found the procedure called to ground
the ICM at the aluminum heat sink plate on the bottom. The
ICM tested fine. However I did notice oxidation on this
heat sink...and on the bracket. It pulls ground between
those two items when it is mounted. I sanded the sink and
the bracket, smeared a film of dielectric grease between
them, this should help the ground situation. Now I just did
this last night, so no long term verification. But after a
test drive...the hesitation was gone. I just hope with
higher ambient temperature during the day...it stays that
way.

If needed...I am going to check the fuel pressure next. I will keep you all updated.
Finally an update. Well improving the ground of the ICM didn't help. The ICM tested fine at O'Rielly's...of course...off the car and cold. I finally tested the fuel pressure. With key on...before start it had 47 psi. When first started...for the first minute or so...the gage fluttered profusely...between 40-47 psi. After the first minute...the gage was still fluttering...but between 40-42 psi...steadily. Once I shut the engine/fuel off (key off) the pressure stayed at 35 psi. Is the fluttering an issue? Or is it due to my lesser quality pressure gage?

At this point...I am still needing help. The origial symptoms still exist.

Thanks!!!

Finally an update. Well improving the ground of the ICM didn't help. The ICM tested fine at O'Rielly's...of course...off the car and cold. I finally tested the fuel pressure. With key on...before start it had 47 psi. When first started...for the first minute or so...the gage fluttered profusely...between 40-47 psi. After the first minute...the gage was still fluttering...but between 40-42 psi...steadily. Once I shut the engine/fuel off (key off) the pressure stayed at 35 psi. Is the fluttering an issue? Or is it due to my lesser quality pressure gage?

At this point...I am still needing help. The origial symptoms still exist.
Do you have an air bleed on your pressure gage? If not, you may have air trapped in the line and this could contribute to erroneous readings, such as “fluttering”. I don’t recall if you replaced the fuel filter, however, that could contribute to the “fluttering” reading also.

Regardless of the fluttering issue, it appears that your fuel pressure is OK. Have you cleaned the TB & plates on both sides, and does it have a smooth opening off idle. Sometimes, when the plates stick in the TB from an idle, the engine will hesitate when they spring open.
do a few "freeze frame" & data record scans and write down the readings, or do a printout. What is the LTFT & STFT @ idle? We are still waiting on some scanner readings.

Do you have an air bleed on your pressure gage? If not, you may have air trapped in the line and this could contribute to erroneous readings, such as “fluttering”. I don’t recall if you replaced the fuel filter, however, that could contribute to the “fluttering” reading also.

Regardless of the fluttering issue, it appears that your fuel pressure is OK. Have you cleaned the TB & plates on both sides, and does it have a smooth opening off idle. Sometimes, when the plates stick in the TB from an idle, the engine will hesitate when they spring open.
We are still waiting on some scanner readings.

Yes the gage does have a bleed...and I had bled it out prior. I had heard about an incident awhile back where the filter media would cause the flutter. The filter and pump are around 6 months old...however I suppose I could have a faulty WIX filter. I think I have another laying around...I'll swap it out...then cut the old one in two to inspect it.

Doesn't seem to be any throttle stickage...very smooth...even while hot.

I thought I had posted the results from the scan...sorry about that. I didn't write them down one by one...but did check them as tested each item...and on every account...they were within range. Should there be any particular items I should pay close attention to?

I have been trying to troubleshoot an issue with my '98 Buick Park Avenue with a 3800 Series II (non-supercharged) for the past 3 months...and need some more ideas. It has around 80K miles on it.

Whenever the car is up to operating temperature (160 degs or higher) it has a tendancy to stumble, more like fall no it's face, when accelerating from a stop. I basically have to feather the gas to get it up to speed...or stomp on it. I say tendancy...because the issue is intermittent. Around 50 percent of the time.

It doesn't have this issue when it is cold...actually runs like banshee until the computer kicks in.

The puter hasn't stored a code (of course that would be too easy). I have done my homework...both on this site and others trying to come up with a solution. So, over the past 3 months, I've loaded my "Parts Cannon" and blasted away. Here is what I believe is a complete list of components that I have replaced to date. I have placed them in chronological order:


MAF (Mass Air Flow Sensor) <It had a slight film on it from my K&N Filter -which I replaced with a paper one>
TPS (Throttle Position Sensor)
Spark Plugs, wires, & fuel filter
All 3 Coils
MAP (Manifold Atmospheric Pressure) Sensor <Replaced the PCV at the same time>
Both O2 Sensors (Front and Rear)
Fuel Pressure Regulator
IAT (Intake Air Temperature) Sensor <thought maybe it was ambient temperature related>
Crank SensorI replaced most of the sensors above due to my research finding that possibly some "could" be out of range without throwing a code.
I removed the EGR Vavle...to make sure it was moving freely. I've been brainstorming continuously...trying to come up with a solution.

Thought about the Catalytic Converter being plugged...then read about the notorious upper intake leaking some coolant into the exhaust and wiping the converter out. The EGR actually doesn't pass through the intake on this one...it is plummed remotely (sort of).

I am so fustrated at this point...HELP!even though the egr does not pass through the cat does not mean that it isnt your problem. usualy when the egr diafram is stuck open it will act up on the cold start and when its stuck closed it will act up after its warm. some are electronical(typicly aftermarket)and they dont realy have these problems but if there is a hole in the diafram it will not work as it should.

even though the egr does not pass through the cat does not mean that it isnt your problem. usualy when the egr diafram is stuck open it will act up on the cold start and when its stuck closed it will act up after its warm. some are electronical(typicly aftermarket)and they dont realy have these problems but if there is a hole in the diafram it will not work as it should.

I tried a new EGR...still having the issue. I think all that is left is having the injectors serviced. Any other ideas before I send them off???

any updates? My 95 has a similar issue. drives great when it cold but falls on its face when its hot and the outside temp is hot

any updates? My 95 has a similar issue. drives great when it cold but falls on its face when its hot and the outside temp is hot

Sorry...the only update I have is that I traded it off.