Well, it may be the ignition module, which are famous for going intermittant at any time - you can obviously check for spark and it's there and when you drive the car - it fails, leaving you perplexed as to the cause. It is located on the left inner fenderwell near the front of the vehicle. Look for a small square module approx. 4" across held by two screws. It's a good idea if possible to use some heat transfer paste on the back - they tend to fail partly because of inadequate heat dissapation. I always carry a couple of spares in the glove box. You could try an auto wrecker and save money - chances are you'll find a newer unit that was replaced on one of the wrecks. Hope this helps you out.