Thread: 1993 3.1 Engine stalls occasionally.

Hi yall. I have a 1993 GP with the 3.1 engine. This engine stalls occasionally while driving. It usually happens after cruising for a while and I have to slow down. So when I'm braking and of course I've take my foot off the throttle the engine just dies. I have to come to a full stop, put the transmission in park, turn of ignition and restart. In the past its started immediately but this last time it would not restart for about 3 minutes, eventually firing up after several cranking attempts.

Ordinarily, the idle seems steady. The problem is rare but scary in traffic. I know these types of problems boil down to fuel or spark starvation. I have not done any tests yet but I wonder if anyone with a similar experience could suggest a likely culprit. Based upon the symptoms I'm not inclined to think fuel starvation is the culprit at least not the fuel pump since the vehicle accelerates and cruises uphill (when its using more fuel). So I'm thinking the crank position sensor but don't know how to test it but I thought cps's failed outright. I realize there are probably plenty of other things I'm not thinking of.

One other thing - I notice sometimes a slight air rush (i.e. vacuum) in the gas tank when I remove the gas cap to refuel.
As I said this is a '93 but low mileage - 63.000miles. Any suggestions much appreciated.

I don't think it's a cps or fuel pump based on your symptoms. It could be idle air control is sticking, or it could be a map sensor or the vacuum routing going to it.

Also, you should be able to restart the car by putting it in neutral, park shouldn't be required.

Could be fuel injectors as well, those are notorious on the 3.1s

Originally Posted by Mitch R

Could be fuel injectors as well, those are notorious on the 3.1s

Thanks Mitch R, that has given me what I was looking for - a pointer to what I should be looking at first i.e. the most likely culprit.

Injectors on these can be confirmed with a resistance test. Take each one and test the resistance between the two pins. Anything less than 12 is considered bad. Anything less than 11 is totally junk.

I tried to start by testing the MAP sensor on the vehicle but there was no way I could get a paper clips into the back of the electrical connector to the sensor. In order to test the sensor off the vehicle I would need a 5V DC power source and a vacuum pump with a gauge to generate specific vacuums. I don't have either of these so I decided to my visit my local auto parts store to price a replacement MAP sensor. If it was cheap enough I would just go ahead and replace. It was quoted as $50 so I decided that was too much for a part that maybe ok.

However the help at the parts store asked me about the problem I was having. I told him and he said he worked on GM W body vehicles from the late 80's/early 90's and said that on those vehicles the torque converter clutch (TCC) would sometimes lock up and when you slowed down the TCC would not disengage and stall the engine. I guess that could be a problem but I don't get any judder or shaking which is what I would expect.

Anyway my list of possible issues is growing. As I see it the list is as follows:-
1. Bad MAP sensor - I still have not found a way to test it.
2. IAC sticking or bad - not started looking at that one yet.
3. Bad fuel injectors - need to test resistance
4. Bad coil pack though this seems unlikely to me because I thought that when they failed they failed completely
5. Sticking TCC - this would be expensive and I don't know how to test.

I anyone has some hands on experience with any of these issues with this type of vehicle any useful input is appreciate.

I had the tcc issue on an old Corsica but never on any of the wbodies I've had. I personally don't think that's it. I would check injector resistance as that is very common on these. It could be the coils or more precisely the ignition control module beneath them, those go bad fairly frequently as well but there isn't any good way to test them. You won't be able to tell if the map is a little off using a multimeter and if it's off a lot you would get a code. Could still be on it a way out.