1994 Bonneville stalling at different rpms

[ricksolo]

Hey guys. My name is rick and I have been rummaging around the site for a little bit now trying to dig up info on stalling bonnevilles.

Ive noticed a lot of posts about stalling bonneville that seem to go unresolved I then started thinking about how I should contribute to the community if I also expect to benefit from the knowledge to be found here.

I will be doing a write up that deals with my particular issues and will see it through from now until the issue is resolved in hopes that when someone else may run into this same problem they will be able to reference this thread. Now for my problem.

Car is a 1994 Bonneville N/A
Bonnie has 129,7xx miles

It recently started acting kinda funky.

As you apply throttle and the rpms build the car seems to hit a rev limiter almost like fuel or ignition is being cut. If you continue to apply throttle eventually the car revs past the "rev limiter" and then shuts off. It will start right back up no problem and will idle fine.

Sometimes this happens at about 3k rpm or 3500rpm other times its as low as 1800-2000rpm.

The car seems to lose electrical power as the voltmeter drops before eventually dying.

A little more info on what has been checked out already:


Battery-Test Passed

Alternator- Test Passed

Ignition Control Module- Test Passed

All 6 Coils have spark

All 6 injectors are receiving signal

No vacuum leaks

No CEL or codes

I cleaned the MAF just after this started happening and it did nothing.

Gas MPG dropped from about 20-21 to 17

Humid days seem to make the problem worse (could just be a coincidence).

I know about the ground bus under the drivers carpet. Its corrosion free and has good contact. lol

I will be checking the fuel pressure just as soon as I can locate my tester.

Ive read that the fuel pump relay can go bad on these cars Im going to test this out but I doubt it is the cause of my problem.

I will be checking/testing the crank sensor as well but I doubt this is the cause of my problem.

TPS will also be checked since it has given me problems in the past but again I doubt this is the cause of my problems.

I am thinking that this could be a MAF issue or even the ECM since things can get real wonky.

Here are some videos to what it does.

This was taken earlier today in park: http://youtu.be/9oFn8tARzu0

This one was taken while driving Saturday afternoon: http://youtu.be/ClJY86ccr-s

If you guys have any suggestions please speak up. In the mean time I will go back to digging around this site.

p.s. sorry for any grammar mistakes. I didn't proofread before posting. Im tired.

[Jrs3800]

I make no promises in my statements... But

There are a lot of scan tools that will not read the 94-95 3800 PCM properly.. Generally when the PCM fails it can throw a P0361( should actually be a P1361 ) Most tools see this as a P0361..

This is a code for a the PCM not signaling for the ICM timing to PCM timing handshake... If the timing control is not handed off to the PCM of the PCM doesn't take control then you will run in module mode timing( 10 * of advance )...

There are grounds on the drivers side as I think you have already found, there is also a set of grounds on the passenger side in the same place.. Those should be checked as well..

It seems more like a Bad PCM, it was common of these to fail with no codes, and fail in an odd manner leaving even the best mechanics scratching their heads..

So check the other grounds..

Check the fuel pressure, should be in the 41-47 Psi range give or take a few..

I actually went through several of these PCM's.. The last one would set off the check gauges at random and would bong you to death out of the blue.. Mine never completely stalled out while driving but would drop the tach like a rock and then suddenly come back... If you started it and let it idle it would stall out like you shut the key off.. More than most it would run a couple of minutes then just shut off..

So it is a possibility with all the stuff you have doing strange crap... However a bad ground can cause a lot of issues, so take a look at the grounds on the passenger side first..

[ricksolo]

Thanks Jrs3800.

Yeah tell me about it. Its pretty much hit or miss with the scanners. Some work, most don't.

I was thinking PCM but want to hold off and check a few more things before condemning it, although I wouldn't be surprised if it is. When the car starts to build revs it feels and sounds just like it hits a rev limiter when it starts to malfunction. Then it soars an additional 1000 rpm before shutting off completely as you can see in the videos above.

[ricksolo]

No new updates as of yet guys but I just remembered that my friend has a 95 buick lesabre, hopefully this weekend we will try swapping PCMs just to see if that makes a difference. I will keep you guys updated as soon as I can.

[ricksolo]

Took the car out for a drive just now. Starting to have second thoughts on the PCM. It has familiar symptoms of a bad ICM. Have any of you guys had any experience with ICMs that have tested fine but turned out to be faulty? If you did how did you figure it out?

[1oldman]

Took the car out for a drive just now. Starting to have second thoughts on the PCM. It has familiar symptoms of a bad ICM. Have any of you guys had any experience with ICMs that have tested fine but turned out to be faulty? If you did how did you figure it out?

I've had a couple of defective ICM's that did not fail until they were hot, but the engine would not fire (the old Magnavox ignition system, not the Delphi system). I would lean more toward what Jrs3800 posted. Ground or bad PCM. I've replaced my PCM twice because the first replacement (remanufactured) was defective. I went ahead and sprung for the new PROM in the PCM while I was at it. It did make a difference, the PROM. By the way, I'm not a "grearhead", this was my personal experience. - BC

[Popcorn]

I have the same car you do and I have the SAME problem, which hasn't been resolved yet. About five years ago (around the same miles as yours) mine started stalling while driving. I happed when warmed up, and it was unpredictable. Finally resolved that by replacing the CPS sensor. This winter it started acting like yours, rev limiter and all. If I let the engine warm up, it ran fine. One day I noticed the Harmonic Balancer was quite checked so I had that replaced. This didn't fix it. I had the mech examine the CPS for
visible damage, but it was fine. With warmer weather, it stopped doing that. So you are not alone!

[1oldman]

I have the same car you do and I have the SAME problem, which hasn't been resolved yet. About five years ago (around the same miles as yours) mine started stalling while driving. I happed when warmed up, and it was unpredictable. Finally resolved that by replacing the CPS sensor. This winter it started acting like yours, rev limiter and all. If I let the engine warm up, it ran fine. One day I noticed the Harmonic Balancer was quite checked so I had that replaced. This didn't fix it. I had the mech examine the CPS for
visible damage, but it was fine. With warmer weather, it stopped doing that. So you are not alone!

Would a Crankshaft Position Sensor/Camshaft Position Sensor cause a "Check Gauges" alert in the Driver Information Center"? - BC

[Popcorn]

Would a Crankshaft Position Sensor/Camshaft Position Sensor cause a "Check Gauges" alert in the Driver Information Center"? - BC

It certainly did in my car, accompanied by chimes sounding four times. If it happened while parked, I could let off the gas peddle and it might not die out and would recover normal idle speed. If it recovered the check gauges would go out. I never got a SES from this problem. I think this may be another failure mode of the CPS. I expect it to return this fall/winter.

[2000Silverbullet]

I have the same problem with my daughters 94 SSEi.
Random stalling and stalling on cold start.
Just before it stalls the tach and speedo jump about 10 degrees and then drop to zero.

Been fighting it for a few years now and am about to give up.
When it first began happening the PCM was changed.
No.
Then the CamPS.
No.
Then the CrankPS
No
ICM
No.
EGR
No
MAF
No

It's in a shop right now and they are still trying to figure it out. The mechanic says PCM.....here we go again!!!
The bill is at $400 now......that mechanic may just have bought that car!!!

[1oldman]

I have the same problem with my daughters 94 SSEi.
Random stalling and stalling on cold start.
Just before it stalls the tach and speedo jump about 10 degrees and then drop to zero.

Been fighting it for a few years now and am about to give up.
When it first began happening the PCM was changed.
No.
Then the CamPS.
No.
Then the CrankPS
No
ICM
No.
EGR
No
MAF
No

It's in a shop right now and they are still trying to figure it out. The mechanic says PCM.....here we go again!!!
The bill is at $400 now......that mechanic may just have bought that car!!!

It could still be the PCM. The first replacement PCM I got was defective. I got a new PROM for the "new" (reman) PCM for it the second time JIC. It was only $50. I'm pretty sure that there are only 3 things that control all the gages. 1) power 2) ground 3) PCM. Guess I'll dig through the FSMs and see what I can figure out. - BC

EDIT: Only 1 common thing - the ground if it's wired like my '93 SSE. I dug through my FSMs. - BC

[1oldman]

I just realized that if the '94 PCM is located in the same place as the '92, you can replace the PCM yourself. It's to the right of the glovebox. Pull out the glovebox liner and the "hush panel" under the dash on the passenger side. Be sure and properly disable the airbags first (remove the fuse [13? - it's labeled] from the fuse box and disconnect the yellow wiring at the connector under the dash on the passenger side) - BC

[2000Silverbullet]

Thanks Brad. I'll keep you posted. I am 1000 miles away from the car now so the shop will have to do it.....

[ricksolo]

Hey guys, I apologize for not providing many updates the last week or so. The car has been sitting in my garage on time out while I contemplated pushing it into a ditch and

Anywho, I ran a few more test on her through out and everything came up within spec.

The fuel and spark would momentarily cut while the car would rev to its new rev limiter of 2000 rpm, however they were not doing it in a matter I would condemn either of them.

Plugs wires etc etc all the usual checks came up fine.

Hooked up a snap on scanner and watched different signatures as well as commands while I tested *dang* near everything I could think of, nothing.

Once again I was back to wanting to condemn the ECM. As a retired tech I can almost count the number of times I have witnessed a bad ECM on 2 hand.

Today I finally limped the car over to my friend's house and took her cars ECM hostage for a few mins.






Like a light switch was flipped. Instantly ran better and the problem went away.

I threw my ECM into her car and her car did the same thing mine was doing.

Glad to say my gut was right the whole time. BAD ECM CONFIRMED.

1oldman, The PCM/ECM whatever you want to call it, the brain box on my 94 bonneville and my friends 95 Buick Lesabre are located under the dash on the passenger side.

There is one plastic cover that needs to be removed. Its literally like 2-3 nuts and or clips.

Then you press on the white tabs that hold the comp in place and slide her out. Takes a bit of tugging and some cussing, but it does come out. lol its really not that bad at all.

Im not sure but I believe the comp is a reman. i have to take a better look at it tomorrow but I didn't really see any GM/Delphi/ACDelco markings on it.

Oh for anyone who has never looked in one of this things, The blue rectangle is the PROM you have to swap over if you buy a new comp.

Once again its late and I didn't proofread nothing, lol So don't criticize my grammar. Thanks guys, I really appreciate the help and info. I hope someone might find the info in this thread helpful someday.

If you guys have any questions speak up.

[ricksolo]

Sorry for the weird angle on the pics. I rotated them in photo bucket but they won't show up here correctly.

[1oldman]

I'm extremely glad you have your problem resolved! There are few things that can get under my skin like a car that I can't get fixed. - BC

[2000Silverbullet]

X2 Bill

[ricksolo]

I'm extremely glad you have your problem resolved! There are few things that can get under my skin like a car that I can't get fixed. - BC

Yeah no kidding. Ive been out of the automotive field for a little over 2 years its amazing what you forget. Any problem I can't figure out now in 2-3 hours MAX I kick myself and think "i should know what the heck this is and whats wrong by now!!!!"

Not to mention the constant double and triple guessing myself, something I didn't do before.

[1oldman]

Any problem I can't figure out now in 2-3 hours MAX I kick myself and think "i should know what the heck this is and whats wrong by now!!!!"

Not to mention the constant double and triple guessing myself, something I didn't do before.

You're doing great! Sometimes it takes me months to "'" kick myself and think "i should know what the heck this is and whats wrong by now!!!!" "'" - BC