1991 Bonneville Rough idle & run when cold

[shilohin]

Hi again.

I didn't test the old ECT sensor as it was difficult to get to, so I just replaced it with a new one. It didn't make any difference. I also replaced the ECM, which didn't make any difference. Hasn't thrown a code yet. Thanks!

[Jrs3800]

This is a start after my Bonneville had sat for over 24 hours...
Notice How it starts and how it idles while cool.. Vid is a tad long... Please forgive the current carnage of the car as it had a new windshield installed..


Does you'd idle anything like this? Faster, Slower... Or the same just runs crappy?

[shilohin]

Hi,

Thanks for posting your vid. I couldn't really tell that yours wasn't running right. However, that gave me the idea of posting my own vid. In my vid, the car has just been started, sounding chuggy and I have indicated on the vid where you can hear the engine surging. Although the vid is only a short one and doesn't show or hear the engine running smoothly, it does run smooth as silk when it is warmed up and does NOT sound like it has a bad muffler like you can hear in the video. Maybe being able to hear the engine run will give someone an idea of what might be causing it. This car has been VERY reliable and has mostly run like a charm.

http://s284.photobucket.com/albums/l...nerunrough.flv

Last year, I had SES light come on repeatedly with a camshaft sensor code. I replaced the sensor about 4 times, each time it would run fine for a few weeks and then throw the same code. When I replaced the timing chain & gears, the sensor magnet on the camshaft had totally disintegrated into a pile of magnetic particles. I replaced it and fixed that problem.

Hopefully someone can help me figure out what my current problem is. Appreciate the help! Thanks!

[Jrs3800]

Wow... That Video does help...

You have a dead on Miss of some sort... Either an injector or you have a Bad coil... I am almost leaning towards the coil..

I think you had said you have replaced that coil pack before, and if so what brand? Also what kind of Plugs are currently in the car?

I am almost tempted to tell you to get a Delco Type 2 Ignition system from the wrecker... Hard to say for sure thats what the problem is without being there to look at it closer.. But its sounding a lot like an ignition problem

In my Vid you can see that I gave the engine a few revs and it didn't skip a beat..

[shilohin]

No, I have not replaced the coil. It still has the original coil that came installed with the car. Here's a photo of the coil that is in the car now:



<p>
This is a coil that I have that a friend gave to me a few years ago. It was pulled from a working 1990 Buick Century with a 3.1 engine:



They both use the same connector but someone told me you HAVE to replace the coil with exactly the same model, which is why I haven't swapped it out with the spare I have. Any ideas?

Also, I have Champion plugs. I installed a new set about 3-4 months ago. The car had some brand of platinum plugs installed when I bought it and they would miss after about 4,000 miles. I got rid of them and installed copper Champion plugs. My first car was a 1968 Buick Riviera GS that had Champion plugs in it when I bought it. Later I replaced them with AC plugs thinking they would be better since they were what GM recommended. The AC plugs would start missing after about 3-4,000 miles so I put Champions back in it and never had anymore trouble. I've been sold on Champion plugs ever since. BTW, when I recently replaced the Champion spark plugs in my Bonneville with new Champion plugs, the old ones had probably 35,000 miles or more on them and you could hardly tell them from new ones. No fouling, not burned, looked excellent. I replaced 'em anyway. Thanks for your help!

[Jrs3800]

Ok here is the deal..

The only V6 offered in the 1990 Buick Century was the 3300 Buick V6, Little brother to the 3800...

The coils you have would work, but the ICM( Ignition Control Module ) will not work with your Bonneville... The Bonneville is a SFI( Sequentially Fuel Injection ) car...

The 3300 V6 was a batch fire MFI system, iirc this system fires 2 injectors at the same time.. The Module from the buick will also be keyed differently..

You would have to have a 3800 V6 ICM to be able to use that system.. The Delco system does fire a bit hotter than the original Magnavox system.. I have ran everything from AC Delco Plugs to NGK TR55 Plugs with good results on the Delco System...

Bosh Plats are a no no with the 3800's..

If you have any questions at all i will be more than glad to help you with them

I also neglected to ask.... Are these the wires on the car now?

If these are the wires on the car, they are all original and most likely should be replaced..

I still your problem in ignition related... Possible coil or wire( if original )

[shilohin]

The spark plug wires were original, yes. I changed them today with some new spark plug wires and no more cutting out. Fixed!

It's really nice to have someplace to seek help with a problem and have friendly and knowledgeable people offer advice and suggestions. And I've learned a few things too. While I always have done my own maintenance and repairs on my Bonnevilles, some things I've never had to work on. I didn't even know the car has an Idle Air Control (IAC) motor, nor did I know it has an Ignition Control Module (ICM). I thought that the ignition was totally controlled by the ECM but it isn't.

Anyway, thanks to everyone who offered advice. Especially to Jrs3800 for coming back over again with more comments and advice. Appreciated muchly.

[Jrs3800]

Originally Posted by shilohin

The spark plug wires were original, yes. I changed them today with some new spark plug wires and no more cutting out. Fixed!

It's really nice to have someplace to seek help with a problem and have friendly and knowledgeable people offer advice and suggestions. And I've learned a few things too. While I always have done my own maintenance and repairs on my Bonnevilles, some things I've never had to work on. I didn't even know the car has an Idle Air Control (IAC) motor, nor did I know it has an Ignition Control Module (ICM). I thought that the ignition was totally controlled by the ECM but it isn't.

Anyway, thanks to everyone who offered advice. Especially to Jrs3800 for coming back over again with more comments and advice. Appreciated muchly.

Glad to be of help... If you have one bad wire it can wreak havoc on the GM DIS system as its a waste spark system... And just like it says it really does waste a spark.... It takes more to fire the plug on the compression stroke and less to fire the plug on the exhaust stroke... So more of the power will go to the cylinder on the compression stroke.. When everything is in good working order the system works very well..

Glad you got it fixed