I have a 95 Gran Prix that when I try to start it I turn the key and the starer doesn't turn and the dash goes dim. As I continue to turn the key eventually the starter engages and the dash lights back up. After it has started it the idle is very sparatic and wouldstal if I didn't give it gas. Also while all this is going on the dash is very dim and the speedometer is ussally around the 10 mph range whle the car is in park. After a while it all passes and the car is fne. I've had it computer tested and they can't find anything plus onc they clear the memory the car will be fine of about two weeks. The battery, alturnator, and starter are all new and working and the only suggestion from the machanic was that it might be the igntion switch since this model and year uses a "pass key" ignition which can go bad. So with all that said, I was wondering if this sounds probable and if there was a way to test the ignition switch before I spend the $350.00 to change it. Any help would be greatly apreciated.
Well anything is possible but.... I feel that line of reasoning is faulty
1. The Pass Key system only prevents the starter from operating, it doesn't shut down any other system.
2. From your description of the problem it appears the starting sytem is drawing current (the lights dim when you try to crank).
3. They "computer test" it but find nothing. Why do they "clear the memory", there's nothing to clear.
4. The Pass Key system has it's own module so it has nothing to do with the PCM anyway.
I feel your problem is in the starting/charging system itself for these reasons;
1. Just because you have a "new" starter doesn't mean it's a good starter. Same goes for the alternator.
2. See #2 above.
3. If memory voltage to the PCM drops too low the PCM has to relearn operating strategies and that may explain rough running on the initial start up.
4. The lights are dim on initial start-up indicating low voltage. This could be because the alternator is turning at to low an RPM to come online. It could also be caused by an overheated battery cable. Low voltage will also cause the engine to run rough.
Okay, all that being said I'm trying to troubleshoot a car online based on your information which ain't easy. Also you say that it runs good for two weeks after they look at it, and that bothers me. My call goes to a bad battery cable or connection. Check the voltage drops both static and dynamic and I think you'll find your problem. If that's not it double check the starter and alternator. Good luck.