3:1 odds its the crank sensor. Usually ignition switch will cause more issues than just stall/loss of tach. Those are classic CPS symptoms. See this thread for my suggestion on making your own harmonic balancer puller: http://www.grandprix.net/forum/ubbthreads.php?ubb=showflat&Number=213845#Post213845 . It's really a pretty easy job, but your first time plan for it to take at least a couple hours. Worst part is the crank bolt. Move your coolant reservoir and fuse box out of the way and go at it from the top, using a long cheater bar. Make sure you clamp some vice grips on the flexplate to prevent the crank from turning.

Would placing the breaker bar against a solid object and bumping the starter an idea on these?

I've heard of guys doing that too. Will only work for removal though, still have to get leverage to torque it back on when finished with the repair.

Doesn't it all come as one piece? That's the impression I got from the dealer guy.

It's the bucking it does sometimes too, with a very audible clicking coming from the passenger side under the hood during the bucking that led him to say ignition switch. Relay getting 12v then 0v then 12v then 0v

No they don't

Here's a good write up on how to change one

http://www.automotiveforums.com/t653340-how_to_replace_ignition_switch_97_03.html

Here's the part in question

I have a grand prix gtp/ it stalls from time to time but I just go get another keyswitch with new keys from oreileys- about 14.00/ I bought lifetime warranty and so far now in 2 1/2 years replace 3 key switches/ the first time my son replaced it/didnt solve problem I said maybe the switch was manufactured bad sure enough it was. so now its I had to replace the key switch twice. it stalls out might wait a few moments then it will start but you can always tell when it goes bad because it will act like trans is kind of slipping sure enough after about a week it starts to stall. I dont know if there is a more serious problem I only know every time it does it I get a key switch and its good to go

Thanks. It is currently at GM for a diagnosis. They have the proper equipment and I am at a loss....I can't just start throwing parts her way. I'll keep you posted.

BTW....a MAF at the dealer is $591. WTF??!! Its a piece of plastic with a couple resistors.

^^That's the dealer for you, Rock Auto has AC Delco MAF sensors for $199.79 (new) and $158.79 (reman) with a $63.00 core charge. I hope they can find the problem with the car.

Japan crisis must be driving up prices, I replaced mine a couple years ago and it was around $150 for the AC Delco MAF.

I found an ignition switch from a 2002 GT. Will it be interchangeable with my 1999 GTP? The 2002 has pass key III and mine has none.

anyone? I will go get it tomorrow if it will work

It should work, as long as both cars have floor shift (some GPs had column shifters).

OK, found a good MAF (so far....been 4 days with no codes), however she still stalls out. I can't decide if it is ignition switch or crank position sensor, or something else.

Stalls when driving sometimes at any speed. TCS OFF light on and loss of tach (sometimes).

The thing is, I can't get it to do this, only happens when she is driving. I wonder if my best bet would be to take it back to the dealer.

I'm gonna say crank sensor. TCS pulls timing to help gain traction if it's getting faulty info from the crank sensor for timing it would turn the TCS off.