Pontiac Repair: chugging /stalling, crank sensor, engine computer

Question
I have a 1990 Grand Am 2.5 the car will run fine for awhile then will start to chug.If I give it gas it will clear up some and run fine for a little while the do it again also seems to do it when taking off from a light .I have changed fuel filter ,fuel pump,spark plugs ,map sensor,fuel injector.also the service engine light came on this evening .I took it to a shop they said it did not drop a code #they had it for 2 days and said they could not recreate the problem ( bull) but 10 min after leaving shop it started again .any ideas would be helpful thanks

Answer
Hey Shaun:

it can be a lot of things. If the service engine light goes on there has to be a code set. Unless there is a major fault in the engine computer. On this I would take a look at the ignition system first. that car was noted for crank sensor and ignition module issues along with coil issues but ignition coils are usually good or bad not too much of an intermittant problem. Being that this car is 20 years old now it could be just about anything it could have a bad ground wire connection on the engine to a bad sensor on the engine the best thing to do it to take it to another shop and hopefully they can induce the problem and see what it going on.. the hardest thing with intermittant issues is trying to get them to happen.. try to give the shop as much detail as possable as to how and when it happens.. It's like going to the dr for an ailment and just tell him/her you don't feel good but don't tell them what and where.. good luck :)