IAC Valve Question

[t93k2500]

My 94 K1500 with the same setup idles at 550 in gear HOT, and cold is about 800 in park.

Something to check...there may be a vac fitting on the back of the TB, between the 2 fuel lines...if its not in use, it will be capped, make sure the cap isnt split open or missing.

That's for my map sensor. My truck has never idled that nice.

 

[454/4X4]

I had a very similar problem to yours on my TBI 454....and my high idle problem (after replacing everything, computer and eprom included..alot of $$$), ended up being a loose intake manifold. 8 bolts on each side of a big block...and on the drivers side, 3 of the 8 were loose, 2 were so loose I thought the ratchet had slipped to neutral when I started backign them out...the rest were snug. MY #3 and 5 plugs came out WHITE...while the rest came out black....

After replacing the gaskets, the difference was instant...im still fighting a running problem, but at least it idles. Cranks up...goes ot 1300...drops after a few minutes to about 1000, and HOT, to 850ish, and 725ish in gear HOT.

Ive got a new Delco TPS, IAC and CTS coming for good measure, I used cheapy "standard" parts when I redid it all last year...better safe than sorry.

 

[t93k2500]

Intake gaskets were done 15,000 miles ago by the trusted local chevy dealer, and I currently have no coolant loss at all. An, interesting unrelated twist, ive been having a stumble/ miss issue for a little while (rebuilding the tbi did not remedy). First start of the morning no matter the condition, I always give light throttle, and the truck stumbles and rpms jump. Its then all clear until the next morning. Tonight, it did not clear itself before I left work, and I pulled the vac line to the egr solenoid. Truck felt like it lost a lot of power, but was able to drive it home without stumbling or missing. Yet another interesting issue.

 

[t93k2500]

Replaced egr valve and egr vacuum control valve (not solenoid; apparently the 4 bolt main tbi 350s shared this with the 454s). All above mentioned issues are resolved. Strange behavior considering the egr valve held vacuum.