check engine light on 95 bonneville

My check engine light keeps coming on, in the afternoon, about 30 minutes after I leave the office. Occasionally the car stutters while accelerating and sometimes even shuts off. I pump the accelerator to keep it running. The mechanics aren't having much luck diagnosing the problem. Can anyone help?

Need more info to help you out. Such as what codes are stored that cause your check engine light to come on, miles and anything else you can think of.

check out the EGR valve...your symptoms sound similar to what i recently had on my 94 bonneville, and the problem was the EGR valve.

this is exactly what my problem is.. but i replaced the egr valve and it still stalls and stutters... is there some special way to install the egr valve..like stuff your supose to do before putting the new egr valve onto the car?

anyone fix this yet?

I am having this same problem with 94 Bonneville.
Dealership just replaed EGR valve -- but still problem remains.

At stop, when you go to accelerate car hesitates, once it works through that bluh, bluh, bluh, it then accelerates fine. At highway speeds, with AC and cruise control on, car will start surging, tach keeps spiking. Seems worse when it is hot outside. And for first few minutes of driving car when cool outside and left to sit overnight, problem is not there..but within a few mintues of driving, if I stop and try to go again, car hesitates.

Took car to indepednet garage, they tried everything and could not find the fix (although they could re-produce the problem).

Some codes that came out when the dealer replaced the EGR valve were: egr valve pintle and heated o2 sensor. The independent said o2 sensor would not cause "driveability" problems as severe as this, but all other systems checked ok (ignition, fuel pressure, etc.).

Am taking back to dealership, where imagine they will soak me for another $$$ (but hopefully fix it right this time).

Would O2 sensor cause this problem? Is there a quick way to disconnect O2 sensor to see if condition improves?

Does it feel like an engine misfire?
You may have a coil going out when the engine temperature goes up.
I would also look at the possiblity of a sticking injector.
There are too many variables right now to pinpoint what is causing the problem.
I have seen O2 sensors cause some minor driveability issues, but nothing as severe as you describe.

Does it feel like an engine misfire?
You may have a coil going out when the engine temperature goes up.
I would also look at the possiblity of a sticking injector.
There are too many variables right now to pinpoint what is causing the problem.
I have seen O2 sensors cause some minor driveability issues, but nothing as severe as you describe.


Not like a misfire, but not getting enough/or too much gas.....

funny is that it works fine if you are accelerating from a roll, but if you stop and then try to go again the car does the bluh, bluh, bluh and you have to feed it gas very slowly to get the acceleration going.

Another question is how to work with the dealership -- they plug the car into computer, read code, sez EGR valve, replace EGR valve, you're fixed....but anyone that starts car up and would try to drive it can see problem is not fixed -- how do I approach dealership with this? Say "unless you can prove the part you are replacing fixes the proble, I'm not paying"? Would they go for that?

Any advice is appreciated.

they plug the car into computer, read code, sez EGR valve, replace EGR valve, you're fixed

If it was that easy, there would be 1 person that plugs in the car and a flock of trained monkeys slapping parts on.
The scan tool (AKA the "computor") will give DTCs and data stream information...but the tech using it has to be able to interpret the information and make a diagnosis on what is causing the problem...is it electrical control, failed part..etc.....
Just because the code is for an EGR valve doesn't mean that the valve is bad...it might have a broken wire inside the insulation that is not sending the proper serial data back to the PCM.

Another question is how to work with the dealership

Thats easy...talk to the service advisor and explain what your car is doing...a good service advisor will even ride with you and have you duplicate the problem so he will have a better grasp on the problem (thats if there aren't 500people waiting to do the same thing behind you)
Make sure he writes down all the information...don't tell him my SES light is on and walk out..take time to explain.
I hate to get a repair order that has "SES light..check and advise" or "cust states car acts funny"......a good write-up sometimes determines the difference on whether or not an accurate diagnosis can be made.

...a good write-up sometimes determines the difference on whether or not an accurate diagnosis can be made.

Agree, also matters on who writes up the work order. Took the car in yesterday, they said the EGR valve was stuck open, so it should have been replaced anyway. Then, they traced the hesitation problem to a "mass air flow sensor." Initial cost estimate was $289, but they knocked it down to about $165+tax after acknowledging that they had not fixed the problem previously. Have not replaced it yet, was not able to leave it overnight to fix the next day.

Mass airflow sensor sound right?

A MAF sensor can cause a hesitation and a surge.

A MAF sensor can cause a hesitation and a surge.


but can it cause these problems?

Occasionally the car stutters while accelerating and sometimes even shuts off. I pump the accelerator to keep it running. The mechanics aren't having much luck diagnosing the problem. Can anyone help?

as I am having the same problems!

or would an 02 sensor cause this or an egr valve? and can they be cleaned if so with what?

thanks

Does the Check Engine light come on?
There are a number of things that can cause the problems you are describing.
It is difficult to diagnos a vehicle over the internet..(hell..sometimes its difficult to diagnos one when it is in front of you!)
I can make a list a mile long of things that could cause what you are feeling...hopefully I can lead you in the right direction and prevent you from spending money that you don't need to spend.
To start, you may have a fuel pump that is losing pressure, sensor that is schewed, secondary ignition misfire or even a trans shift control problem.
If you came to me, the first thing I would do is ride with you and get you to show me what the car is doing.
Sometimes a simple road test with the customer will lead you right to the problem.
Next would be to hook up some test equipment and drive the car again and watch sensor parameters while the car is acting up...that way I can see what IS and IS NOT causing the problem and hone in on the root cause.
Next is to recommend a repair and then drive the car again to verify the repair.
If you give me as much information as you can, I can narrow down the causes of the problem and lead you in the right direction.

with me the problem does not happen every day or even every week..just when it feels like it...I get the ses light on start up at times at other times it won't show up for weeks ..as far as th car studdering and dying ..as said before it is not routine..but it does happen..and when it does..it trips the SES light I have changed the ignition moduel and fuel filter...I have taken it to auto zone to have diagnosed but because of my year model..they could not!

I have a 94 se!

I purchased this car used about 8 months ago..the first few weeks i got it I had problems with it cranking and not starting..replaced the ignition module (had it tested and it failed)and that hasn't happened since...and everything has worked fine until the past month it first shut completely down on the interstate while driving..got the SES....pulled over and it started right up...It hasn't completely shut down since..but it has studdered and i pumped the gas it and it kept going..

sorry for writing a book..but just giving you some background!

Does it set any trouble codes? If so, which ones?

autozone can't test my bonnie because of the year (94) and the last time I took it to pontiac they said no codes were stored?

but I do get the check engine light!

I know this will sound crazy but I just sold my 94 and we went through this dying stuff and all for almost a year. No one could figure out what was wrong. I spend close to $1,000 on it and finally fixed it myself. It was the Fuel Pump Relay under the dash on the passenger side. I did ECM's...coil paks, plug wires and plugs. Mass air flow, TPS, EGR, Fuel pump...fuel TANK, Fuel filter...on and on....this was the dealer doing all of this. Then I fixed it with a $3 relay from Autozone. It never did it again. We just sold it and bought a 97 SE a few weeks ago.
Rob

I know this will sound crazy but I just sold my 94 and we went through this dying stuff and all for almost a year. No one could figure out what was wrong. I spend close to $1,000 on it and finally fixed it myself. It was the Fuel Pump Relay under the dash on the passenger side. I did ECM's...coil paks, plug wires and plugs. Mass air flow, TPS, EGR, Fuel pump...fuel TANK, Fuel filter...on and on....this was the dealer doing all of this. Then I fixed it with a $3 relay from Autozone. It never did it again. We just sold it and bought a 97 SE a few weeks ago.
Rob
Wow How hard was this to get to? I will try it thanks

It was really easy to get to. It is on a sort of panel under the dash (glove box) right up against the fender on the passenger side. It is a little metal relay that pushes in on that panel.
Rob

ok these are teh codes i got when i got it scanned....anyone canh tell me what they mena if possible!

740 torque Converter (traction control?)
361 EST line not toggling
321 no 18X ignition pulse (crank Sensor)
101 Mass Air Flow Failure (maf) which i took off while celaning the throttle body...that's how this code could have been set!

thanks

The dealership took the car in again (they had replaced the EGR valve when the original code was set), this time they promised they would fix the hesitation AND THEY DID! They traced it to the Mass Airflow Sensor (MAF). The car runs like new! EVen with 90K+ miles on it, it GOES now when you put the pedal down -- no hesitation, it's GREAT.

Good luck to all and thanks for all the advice!

Something to consider here. The computer sets codes for several reasons, but the bottom line is simple. The ECM compares sensor readings to what is programmed into it, comparing sensor readings, and comparing them to established parameters in the software. If the EGR valve code is set, it is because the EGR sensor "readings" "appear" to be off. The software could have been corrupted, the sensor itself could be intermittent, other comparative sensors, such as the TPS, airflow meter, or any other engine sensor used to calculate load could be the culprit. Simply "knee-jerking" to what the computer says is indicative of a thorough misunderstanding of how the system operates. My dog could fix cars if it was that simple. It is also possible for plug wires to cause an EGR code if the engine's surging is caused by this. Think about it; the engine surges due to the plug wire condition, the computer thinks the EGR valve is not open wide enough to cause that, it therefore "thinks" the EGR valve is then the cause. The computer cannot test plug wires, it can only guess at what is causing the miss; if it sees surge, it compares this condition to the EGR valve position, assumes the EGR is at fault due to "multiple" misfires, and reacts. The tech also reacts since he is as uninformed or as stupid as the computer is and replaces the indicated part at your expense. Voila, a misdiagnosis, an unhappy customer. The vehicle's systems are not the problem, techs are. My advise: the next time your vehicle is in the shop for something like this, insist that the tech prove to you that he has correctly diagnosed the problem and is replacing the correct part. Any time I dealt with customers, I explained to them the problem, how it affected the vehicle's performance, and showed them the defect. It is ok to play stupid here. If you do not understand what is happening, insist that the tech show you. It is his responsibility, nee his obligation, to explain, to your satisfaction, what has happened. Informed customers were my best customers. The more questions they asked, the better I could explain the problem, making the "sale" easier. Tell the tech that you want to see what the computer is telling him. The computer will display a freeze frame display of the events surrounding the event that set the code. If he thoroughly understands the event, he can explain it to you. If he cannot explain it to you, he cannot properly fix the problem. I will assist in any way I can. My apologies for climbing on my soap box. Ray

740 torque Converter (traction control?)
361 EST line not toggling
321 no 18X ignition pulse
101 Mass Air Flow Failure

I also have a 1995 Pontiac Bonneville with a check engine light on.....none of the local parts stores has a scanner that can get the codes (supposedly)...Is there a way I can get the codes myself at home? That is....maybe turning the key on and off three time such as some other car makes?

95 was the year they crossed between a OBD 1 and OBD 2. Although the connector is a OBD 2 it's actually a OBD 1.5. You will need a scanner that is capable of scanning a 95 and Autozone will not have that. You'll have to either take it to a mechanic or the dealership.