I've heard that the GM security keys have a tendency for the little security chip, which makes physical contact with the ignition switch, to wear down over time. This can cause this kind of intermittent problem.
The first thing to try would be a newer key if you have the extra set still, or to visually inspect it. If that's the problem, you'll need to get a new key from the dealer.
The risk would be that if the problem is only with the key and not with the existing ignition switch, you would still experience the same problem with the same key.
This is only a guess based--I've heard about this problem with GM cars with those keys. It's unfortunate that the keys are so difficult to replace.
Good question! I'd call the dealer and ask, because I have a feeling it's a dealer-only part. If the only way to get new keys is to get them with a new ignition switch, then that would certainly fix the problem--but it's an expensive part, I'm sure.
I don't believe that a problem with the key will cause for the car to die if it is already running. Could definitely be fuel-delivery, but could be a host of other problems. Sounds like you need a good shop with a diagnostic technician who knows what he's doing.
The new ignition switch would come with a new set of keys but I had the key chip go out on my wife's seville and it wouldn't start period, Remember if the car is turning over then the chip is working because it's a security system lockout, Maybe it needs a tune up.
well its had alot of stuff done to it and still no one knows whats wrong with it even replace a fuel pump and they also change something on it that was suppost to be a recall on something i cant remember