Chevrolet: engine RPM up and down, maf sensor, vechile

Question
I have a 90 Breetta 3.1lt, with the engine running in park the RPM goes from 1200 to 1000 and back to 1200 every few sec.  I have changed the following items spark plugs, plug wires, thtottle position sensor, and MAP sensor.  Also after the engine gets warmed up sometimes it will die and will not restart for 15-20min.  If you are driving the car and it dies when you get restarted as soon as you put it in gear it dies.

thanks brent

Answer
Hi Brent, There are several things that could cause these symtoms, you could try the MAF sensor in the air filter box. This vechile had a problem with a broken wire in the harness from the computer to the engine that caused surging. I would suggest that tou get it put on a diagnostic machine, to narrow down the problem. It will save you money in the long run. Because replacing sensors that are not defective can get expensive. If you need more help, just let me know. Thanks, Keith.