Idling issue. MAP or IAC?

[osbornl1]

Trucks 89 v3500 454 tbi. 4 speed.

It starts fine and will sit and idle for 5-10 mins then stumble and die. It drives fine. Even crusing at 65-70 it runs fine. Now if I come to a stop sign or stop light I have to keep blipping the throttle or it dies.

Any ideas?

Oh and the previous owner messed with a screw on the front of the tb that's by the throttle. The more I screw it I'm the more open the butterfly's are etc. about where should these be set? Completely closed? Slightly opened?


Thanks
Larry
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[gchemist]

If it does it only after it's hot and driven, I would suspect a sticking EGR valve. Remove it and clean it. Reset the air idle valve too. The tip over time needs adjusting for proper air flow at idle.

[osbornl1]

Where is the egr valve located and what's the safest way to clean it.
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