1991 5.7 TBI stalls when hot

[studbeefcake]

My 1991 Silverado is having issues idling when hot. It will stall whenever you put a load on the engine like sitting at a red light in gear or turning the steering wheel in park. My first suspect is the idle air control valve, I have tested the resistance according to the instructions in the hands manual and it tested as good. I also unplugged the IAC while it was running which had no effect the truck continued to run. My mechanic friend says its probably the TBI gasket but I am not sure what to think.
What should I start with?

 

[woody31]

is the check engine light on?? check all vacuum hoses,,spray around the base of the tbi with carb cleaner to detect a leak,,,how long has it been since it had a tune up,,check timing,,ect,,ect,,

 

[studbeefcake]

No check engine light, it could probably use some tune up but I'm not sure if that's related to the stalling because the engine runs very well except under the conditions where it stalls

 

[91Bluestreak]

Check your igntion control module under the disty cap. Most parts store can test it. It controls the fuel injectors aswell.

Cowl Induction Burban

 

[Rusty Nail]

Ever heard of "vapor lock"?

 

[SAATR]

Ever heard of "vapor lock"?

You don't get that with in tank electric pumps. The old mechanical pumps had to suck the fuel from the tank, so if the fuel line overheated and the fuel started to vaporize in the line you would get pockets of nothing but vapor, which would cause stumbling and stalling. It's extremely unlikely in a pressurized fuel system.

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[SAATR]

Even if the resistance of the IAC tests good, it could still be sticking. I would clean the passage thoroughly and try it again. You may need to do an IAC reset to verify whether or not it's actually working. Google TBI IAC reset and you should get some info. It's a given that you've checked for vacuum leaks, have good fuel pressure at hot idle, etc.

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[Keepinitoldskool]

Sounds like a vacuum issue of some sort. I would start with some good quality carb cleaner and spray to check for leaks.

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[Big98z71]

How many miles on this motor? Look at the side of the ignition coil, does it look burnt or have a lot of gray color to it?