Pontiac Repair: 97 Pontiac Grand Prix SE 3800 code p0302, vacuum leaks, pontiac grand prix

Question
Says cylinder #2 is misfiring... we have took it to the mechanic.. changed everything on the list plugs, wires, coils, check for vacuum leaks, check injectors, checked fuil pressure.. alll of it.. my check engine light stays on. and we just changed the oil but the change oil light comes on only when it acts up... like when i picked it up from the mechanic today it had the shake when I crunk it. after it sat all night for like 7 hrs it crunk like  a champ.. and drove perfect the whole way home. it only does it now and then and the check engine light always blinks when it does it. my mechanic thinks the computer is bad. What should I do... I love this car and only just got it.. I want it fixed.. we also put a new water pump on it and he checked the radiator... What next....thanks

Answer
Hi jenny:

well an engine needs 3 things to run. fuel,spark and compression. the fact that the issue comes and goes it would rule out a compression issue which would be a mechanical failure of some sort. so it leaves fuel and spark. you could have a fule injector that is bad and causing the issue or on the spark side a coil that is bad. yout could have a bad electrical connection going to the injector or at the ign ition module.. The fact that it's intermittant is the problem. A technician can really only pin point the issue when it's happening. so if you take it i n and it's not acting up it's really hard to find the problem. Goood luck :)