PontiacBonnevilleClub.com

What could the problem be when my 1993 Bonneville SE will start and then immediately turn off?

I went out to my car this morning to go to work and this happened. I tried again and again and it would turn over/crank but then immediately the RPMs would plummet and it would just cut off. Even if I kept my foot pushing down partially on the gas pedal eventually it would cut off. It would only stay cranked for a few seconds.

Some things that happened in the days/weeks leading up to this:

1. The car would often stall in the first 5-10 minutes of driving it after starting it up and generally it stalled when coming to stop. During this time the check engine light would be on but then go out after running for 10 mins or so. Also during this initial 5-10 minutes I could push the accelerator pedal all the way to the floor but the car would not respond properly; it would only very slowly speed up until eventually, as if a 30 second delayed reaction, the car would finally respond by accelerating quickly.

2. Other times after initially cranking the car it would idle much too high when the car was in a stopped position, especially when in the "park" or "neutral" gears, but I found that if I turned the car off, then restarted it the too high idling problem would go away at least temporarily.

But now as I said above my car will start then immediately turn off, Any thoughts on what might be the cause?

Thanks!

-Bobby

Try the following and reply back on here with your results:

1. Unplug the mass air flow sensor and see if the vehicle runs any different. I had a different make and model car at one point I was working on that was a 93 Ford Taurus 3.0 OHV engine that had a bad mass air flow sensor. It did the same exact thing you are describing.

2. Check fuel pressure. It is possible that the fuel pump may be failing. Could also be a bad or dirty fuel filter.

3. Take some carb cleaner and have some one start the engine and try to keep it running long enough for you start spraying some carb cleaner around motor checking for potential vaccuum leaks.

Pull the codes. They can definately help point in the right direction.

http://www.pontiacbonnevilleclub.com/fo ... =51&t=8689

Thanks for the response. I will give these recommendations a try today and post my results. I will attempt to pull the codes as well and see what I get.

So the first thing I did was disconnect the Mass Air Flow Sensor and attempt to start the car. It started up at first and appeared to be running ok then about 4 seconds later the RPM's dropped and the car cut off. Tried to start it a couple more times but just got worse to the point where it wouldn't really start. If I let it sit for 5 mins it will start but then cut off again.

So next I grabbed the codes and here is what I got, three codes in this order:

22 Throttle Position Sensor Circuit ( Signal Voltage Low )
34 Mass Air Flow Sensor Circuit ( Grams Per Secone Low )
39 Torque Converter Clutch Problem

As I said I had been getting service engine lights in the weeks leading up to this problem.

Stevew I wasn't sure how to check the fuel pressure as you suggested or how to know if the fuel pump is failing. I suppose the only way to check the fuel filter would be to remove it, inspect and replace if needed which I didn't have time to do today.

So now that I have the codes any further suggestions? Not sure what to do about the TPS code. I suppose I could remove/clean the MAF sensor or replace it. As far as the torque converter clutch problem I have no idea.

Any suggestions will be greatly welcome. THANKS!

-Bobby

When my '95 SLE did this, it was the PCM. The problem with the PCM going bad, is that you can no longer trust the codes it displays. Mine would set five or six codes that were simply nonsense. If nothing else seems to fix it, perhaps someone on the site has a known good PCM they can loan you or sell cheap? Junkyard PCMs can usually be had for less than $50.

Well after making my last post I removed the MAF sensor and cleaned the wires and inside very well with a q-tip soaked in rubbing alcohol. Then I reinstalled it, attempted to start the car again, and low and behold it started and stayed running! After letting it idle for a few minutes I took it for a spin around the block and back. It seemed to run like normal.

The service engine light did come on and off for the first 5 minutes or so of driving and then went out; same as what it has been doing the past few weeks.

I had to turn in with daylight running out but I plan to pull the codes again tomorrow to see if the MAF code 34 goes away. However the car does run now which is good news.

Still I would love to hear anyones feedback/suggestions on codes 22 (TPS sensor) and 39 (torque convertor) which I also received.

Thanks...

Remove the negative connection from the battery first, then drive it and check for codes after a while. That will clear the codes so you don't just have the same ones repeated back to you.

The check engine light is still coming on and the car is driving now but still noticing some problems with the idling especially upon initial start up.

The only code it is giving now is 22 which is the the Throttle Position Sensor Circuit ( Signal Voltage Low ). I have no idea where this sensor is located or what to do about this. Anyone have any tips on this?


Thanks,
-Bobby

p.s. - I also installed a new fuel filter as multiple people suggested this to me based on the cars symptoms.

I would suggest replacing the TPS with a new AC Delco or Delphi unit. They are a bit pricey, though! The TPS is located under the throttle plate, right above the exhaust cross-over. You will most likely have to remove the throttle plate assembly from the intake to get the screws out.

Unless someone has a better idea?

I usually take the thermostat housing off to get it out of the way of TPS access. It's much less involved than removing the throttle body.

Well I replaced the TPS sensor and it seemed to fix my problems with the car starting and then turning right back off. The car starts fine now and idles around 1,000 rpms. Even after sitting for a few days (which was when I used to see the problem the worst) the car starts right up first try. However the "service engine soon" light is still on and a new issue has arisen.

The new issue is that at highway speeds, say 55+ , if I remove my foot from the accelerator pedal the rpm's do this funny thing where they oscillate between 1,000 and 2,000 rpms. In other words while on the highway if I stop pushing on the gas and just coast, as on a downward hill, the engine starts revving up then slow down, then revs up then slows down, almost perfectly between 1,000 and 2,000 rpms. It does this fairly quickly, probably once every couple of seconds.

Also my cruise control stopped working.

As far as the engine code goes it still is giving me code 22 which is the TPS Circuit. And yes I disconnected the battery and reset the codes, I'm not just getting the old codes, the engine light is in fact still coming on.

So any guesses on what the problem could be?

Finally I might add that one of the hoses I had to swivel out of the way to install the TPS sensor, (It was a bendable hose, believe it may be the oxygen hose?) it does not seem to attach correctly or at all for that matter to the engine, almost as if a clasp or pin is missing. I mean It was just kind of resting in the hole it was in, there were no attachments. I will attach a picture later today since I can't really explain and perhaps someone can give me some feedback.

Thanks everyone for all the help so far.

p.s. In summary I have done the following so far: cleaned the MAF, replaced the fuel filter and replaced the TPS sensor.

Any picture yet?

I would check your PCM fuse, it should be located under the dash on the passenger side right next to the PCM itself. You've got to remove the hush panel to get to it. I got a couple screwy codes and cruise stopped working when mine blew... I think it's a 10 amp if I remember correctly.

FWIW there should be a hose clamp keeping the air hose (between air box and throttle body) in place on BOTH ends.

These:

EDIT: Erp.. Just noticed it was a zombie thread, sorry for reanimating it.

OLD THREAD FROM 2010 - BC