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.
