I'm having a terrible time with my 93 Jimmy, and I thought that someone here could help me.

Problem - Starts up fine and runs for about 15 to 20 minutes, then the engine just shuts off. If I wait for about an hour, this problem repeats itself. It's not overheating, and no warning lights come on. My mechanic was kind enough to rescue me when I was stuck, and he checked to see if motor was getting fuel and spark. Apparantly it was getting both. We had it towed to his shop, where it has been all week.

Things Mechanic Has Replaced

Fuel pump and filter
Fuel relay
EGR Sensor
Coil
Spark plugs and wires
Distributor Cap
Rotors
Ignition Module
Fuel Injection spider
Computer

He has also put it on his diagnostic computer, and nothing comes up as being wrong. My mechanic is highly rated in my city, and also a trusted friend of mine. He is totally frustrated about my Jimmy, and refuses to quit on it. Any ideas or suggestions from anyone would be greatly appreciated at this point!

Have them check fuel pressure.

I have a 93 Jimmy and it had lost the operation of 3 of 6 cylinders- it needed a complete replacement of the injection system and now runs fine but will tend to stall on hard deceleration/braking but that is probably an adjustment. Is yours deceleration/acceleration dependent

You don't have a problem with your Jimmy.
You have a problem with your Mechanic.
He has socked you for probably $1600 by GUESSING at what's wrong and he's still no closer to fixing it????
With "trusted freind" like that you don't need enemies.

I'd suggest you try a good GMC dealer - that is what I did and the results were very satisfactory but cost about 3K. But be aware that a lot of new parts in an old car make it a theft target - thieves tried to get mine (without success but doing 1.5K damage)

Mine is doing something almost identical. It does run for over 20 minutes, but when it stalls it won't start and has stranded me too many times. If you have figured it out, I would appreciate a post to let me know what it was.

I sympathize with you...it must have cost you a fortune already.