Bonneville stalls

I have a 1998 Bonneville with 133,678 miles which stalls when it is cold. I have a chip on the engine and I am wondering if this is causing the problem. The chip has been installed for about 8 month and now that it has been removed I can tell it did really work.
I have a guy testing the normal parts that would cause the stalling but so far he can't find any bad parts. After restarting it runs fine. Any answers?

could be maf sensor and you may want to check and see if your getting blue spark if yellow not good. also i would the fuel pump on the psi if that checks out right then go to fuel filter then i would have coil pack and checked at autozone unless you have a dist. cap? is your check engine lite on?

1st thing you may look at is engine temp sensor,if its out of specs it could be
telling computer the engine is warm on a cold start.like scapper mentioned
checking fuel pressure easy enough to do.

Good luck

Thanks for your answers.
No Engine light on. All sensors on engine have checked out OK. Fuel filter was replaced back in Feb. I did noticed that when the tach nettle starts to jump up and down I can press down on the brake and it goes back to idle and stays there. Coil packs were installed in Feb., new spark plugs & wires, upper manifold kit, lower manifold gasket and O2 exhaust sensor were all replaced in Feb. This problem of the tach nettle jumping has slowly been a problem to were I am thinking vaccume power booster is the problem, will check it.

Thank Again, you have given me more ideas!

Thanks for your answers.
No Engine light on. All sensors on engine have checked out OK. Fuel filter was replaced back in Feb. I did noticed that when the tach nettle starts to jump up and down I can press down on the brake and it goes back to idle and stays there. Coil packs were installed in Feb., new spark plugs & wires, upper manifold kit, lower manifold gasket and O2 exhaust sensor were all replaced in Feb. This problem of the tach nettle jumping has slowly been a problem to were I am thinking vaccume power booster is the problem, will check it.

Thank Again, you have given me more ideas!

is your brake pedal hard to push down if so you do have a problem with booster but i'd go ahead and check the hose running to it.

good luck.........

is your brake pedal hard to push down if so you do have a problem with booster but i'd go ahead and check the hose running to it.

good luck.........


It is easy to press down on the brake pedal. I can stop the tach nettle from going from almost stalling to 2000 RPM by pressing down on the brake pedal hard 4 times, the tach goes back to idle and run normal. I think you are correct on the hose which I will check today. I hope it isn't the booster or worse.

Thank You, Scrapper

Thats not a chip... I bet its plugged into the TPS and or the IAT Sensor... Its not a performance anything in any manner or form... The only real way to get more performance out of the car is to alter the computers tables... I hate those gimmick chips... ( adds 20 HP ) its a bunch of crap.. And there is only so much timing the engine can run on the stock tune..

I'd say if the supposed performance chip is plugged into the TPS, get rid of it first to rule it out as an issue.. Make that the first thing you do...

Thats not a chip... I bet its plugged into the TPS and or the IAT Sensor... Its not a performance anything in any manner or form... The only real way to get more performance out of the car is to alter the computers tables... I hate those gimmick chips... ( adds 20 HP ) its a bunch of crap.. And there is only so much timing the engine can run on the stock tune..

I'd say if the supposed performance chip is plugged into the TPS, get rid of it first to rule it out as an issue.. Make that the first thing you do...

The so-called chip was unpluged for the last 3 days trying to find out why the engine was stalling, I could feel the change in the engine without the chip just like it was before I first put it on. Push down on the gas was like pushing against a brick wall with very slow engine response. I now know why it was stalling, the vaccume hose from the engine to the brake booster has a hair line crack. From what I found out after the brake pedal was pumped the crack in the hose closed up.
After I replaced the hose and reinstalled the chip there was much better throttle body response. If the chip doesn't work then why is the response so much better? My brother has a 1984 Buick 3.8L and he has driven my Bonneville, he first noticed that it was hard to push the gas pedal and slow response from the engine. His car has much better response then my car without the chip. All I have to do is tap his pedal and off it goes. Before the chip on my Bonni I would have to press hard to get it to move. NOW with the chip it's like my brothers Buick. Can't explain it but I think the chip does work.

I am glad that you found the hose from the booster to the upper intake, as that is a problem and will cause stalling as the MAF can't read that incoming air..

as for the chip, Is it indeed plugged into the TPS and the IAT? My feeling is that its simply altering the IAT and TPS for more fuel and more timing... If this is whats its doing it will give you more snappy response...

But your shifts are all still the same per the PCM'd maximum shift RPM and Speed.. You have Maximum timing so the PCM can only go to that point regardless.... as well you have a 4T65E, the 4T65E uses a Pressure Control Solenoid to control line pressure, this system is very dependent on the TPS... But again it can only do so much..

The electronic dohickey that you have attached is playing with the TPS and IAT to alter fueling and IAT for timing thats giving you a little more off the line...

Honestly I think if you were looking for performance I would be more willing to recommend a good tune or a canned PCM like one Intense would sell.. I think you would almost be impressed...lol

At current I am running a 97 PCM on my 95 series II Bonneville( Going to update to the 98 very soon )... Running a Pontiac GP GT Tune +2* of timing, a little extra added fuel, 87 Octane no knock.. 195 fan turn on, 185 turn off, 180 thermostatat, Ported Lower Intake, Intake ports on the head are kissed to get rid of the step... Fuel cut off set at 6300, shift point is 5900 which means it will shift at roughly 6100... and this car is averaging 22 in town and 31 on the road...

There is just a lot you can do to these cars... :cool:

also if you have never done this, Clean the MAF with some CRC MAF Cleaner and see if that brings some more response back... Sometimes a Dirty MAF can slow down the throttle response as well..

I am glad that you found the hose from the booster to the upper intake, as that is a problem and will cause stalling as the MAF can't read that incoming air..

as for the chip, Is it indeed plugged into the TPS and the IAT? My feeling is that its simply altering the IAT and TPS for more fuel and more timing... If this is whats its doing it will give you more snappy response...

But your shifts are all still the same per the PCM'd maximum shift RPM and Speed.. You have Maximum timing so the PCM can only go to that point regardless.... as well you have a 4T65E, the 4T65E uses a Pressure Control Solenoid to control line pressure, this system is very dependent on the TPS... But again it can only do so much..

The electronic dohickey that you have attached is playing with the TPS and IAT to alter fueling and IAT for timing thats giving you a little more off the line...

Honestly I think if you were looking for performance I would be more willing to recommend a good tune or a canned PCM like one Intense would sell.. I think you would almost be impressed...lol

At current I am running a 97 PCM on my 95 series II Bonneville( Going to update to the 98 very soon )... Running a Pontiac GP GT Tune +2* of timing, a little extra added fuel, 87 Octane no knock.. 195 fan turn on, 185 turn off, 180 thermostatat, Ported Lower Intake, Intake ports on the head are kissed to get rid of the step... Fuel cut off set at 6300, shift point is 5900 which means it will shift at roughly 6100... and this car is averaging 22 in town and 31 on the road...

There is just a lot you can do to these cars... :cool:

also if you have never done this, Clean the MAF with some CRC MAF Cleaner and see if that brings some more response back... Sometimes a Dirty MAF can slow down the throttle response as well..

The chip is hooked up to the IAT sensor only. Thanks for the tips, I will replace the PCM in time but right now it will have to do. I have a blown oil pan gasket I need to replace, second one in 2 years. Going with Fel-Pro this time. Never thought of cleaning the MAF sensor, thanks ! :banghead:

In that case I know exactly what that little box is... some of the others have done the same with a 60 cent resistor... what it really does is tricks the PCM into thinking its getting a lot of cold air, this helps keep the timing tables maxed out...

For the oil pan gasket.. Felpro is pretty good and is what I use when i replace the gasket.. What I usually get is the Lower Conversion Kit... Most of the time I can get the kit cheaper than just buying the oil pan gasket...

When you reseal this time, make sure the block surfaces are as clean as possible free of any oil... Place dabs of sealer at the corners of the timing cover and the rear plate... You'll see where these parts come together and create a seem... Place dabs there and install the new pan and gasket... Should stay leak free..

In that case I know exactly what that little box is... some of the others have done the same with a 60 cent resistor... what it really does is tricks the PCM into thinking its getting a lot of cold air, this helps keep the timing tables maxed out...

For the oil pan gasket.. Felpro is pretty good and is what I use when i replace the gasket.. What I usually get is the Lower Conversion Kit... Most of the time I can get the kit cheaper than just buying the oil pan gasket...

When you reseal this time, make sure the block surfaces are as clean as possible free of any oil... Place dabs of sealer at the corners of the timing cover and the rear plate... You'll see where these parts come together and create a seem... Place dabs there and install the new pan and gasket... Should stay leak free..

Thank You Very Much, Jrs3800!

It is easy to press down on the brake pedal. I can stop the tach nettle from going from almost stalling to 2000 RPM by pressing down on the brake pedal hard 4 times, the tach goes back to idle and run normal. I think you are correct on the hose which I will check today. I hope it isn't the booster or worse.

Thank You, Scrapper

so it was the hose huh? was it unhooked or plugged or just off or split? anyway glad you found your problem.

so it was the hose huh? was it unhooked or plugged or just off or split? anyway glad you found your problem.


Yes, it was the hose. There is a crack at the engine end of the hose, I replaced it with a fuel line hose. Thank You for your help Scrapper

Now I can get down the street
without stalling.