Oldsmobile/Buick Repair: 92 Olds 88 Royale occasional no-start & dying, independent mechanics, jumper cables

Question
My 1992 Olds has 106,000 mi and has been well taken care of with 3000 mile servicing since it was new. This summer it suddenly became unreliable, occasionally failing to start. Twice it died when I slowed for a stop light and to turn a corner. It might run fine for a week or two and then suddenly not start.  It usually eventually starts if I sit there a while or if someone comes along with jumper cables. I might try  10-12 times and it might start on the 13th try. I sometimes, but not always, have better luck if I let it sit 5-10 minutes between tries.
My mechanic says they have to catch it when it won't start to diagnose it. They "caught" it and replaced the idle air control motor, but that did not help. They tried again and told me it was in the anti-theft system (my key has a chip in it) and I should take it to a GM dealership. They gave me "pass key system calibration-pass key code 58" to give the GM dealer.  The GM dealer kept the car several days and told me there is no code 58 and to come and pick up the car because they didn't know what to do with it.
My nephew said he corrected a similar problem by replacing the fuel pump relay.

Any ideas?  

Answer
Hello Lee,
A couple ideas.
First, though, your mechanic did exactly what needs to be done. Intermittent electronic problems are probably the absolute hardest to work on, because when they are not happening, they just DO NOT exist.
It is great that they found a code 58, because that is probably a code that clears itself once the problem is corrected, in your case, when the car recieved a correct signal from a good key. I only wish the dealership had given more thought to it. I have dealt with dealerships that seem to think if a person isn't a dealership mechanic, he doesn't know what he is talking about. The truth is, there are many many independent mechanics that have a vast amount of knowledge and experience. I myself have even attended the same "factory" training as the dealership mechanics, usually with a class of them.
At any rate, you have another key for it, try using it, or get another made.

Talk to the service manager again, and see if they have a service bulliten on that problem.

Van