I'm not sure if you can see in the pic but the PO used electric tape and a washer on the TB, presumably to keep the butterfly valves open a little bit more. According to the sticker it says the idle speed on EEC-IV is not adjustable, so why is there a screw there and what do you think the point of this rigged up tape/washer job was? I want to take it off but i'm afraid he put it there for a reason. also the screw has threads on both ends and there is nothing to turn it with. Suggestions?

460 Throttle Body with washer taped on

 

You could remove the washer, drive it around, and see how it goes. If you notice a significant difference put it back, and take it to a mechanic to get the root cause fixed.

The set screw might have a small hex hole in one end to facilitate turning it.

 

The screw is to set the minimum throttle opening so the butterfly doesn't rest against the inside of the bore. Beyond this base idle setting, the PCM (computer) will control idle speed as needed using the IAC (Idle Air Control) which bypasses a variable amount of air around the throttle to maintain idle speed as engine load changes.

The IAC valve can stick and fail to open, which causes a low idle and usually stalling too, so sometimes you'll find that people cure that problem by adjusting that stop screw. The correct way to fix that is clean or replace the IAC valve. That screw can be turned with vice grips or just cut a slot in the end of it for a screwdriver, you're not supposed to mess with it but adjusting it slightly won't hurt anything in my experience.

I'd take off the washers and see how she runs. If it stalls out and dies then try cleaning the IAC valve with some carb cleaner.

 

Thanks for the help yeah cleaning the IAC was on my list of things to do anyway.

On a separate note: My factory air filter box has a hole drilled in it like it is supposed to accept an IAT Sensor or something. I know the MAP sensor is over by the heater core but is this truck supposed to have an IAT sensor? i havent seen one referenced. the only things that i know it has are:

MAP sensor
TPS
Coolant Temp sensor
PIP
Crank
O2

 

Your truck does not have a Crankshaft Position sensor. That information is derived by the PIP sensor. Yes there is an IAT/ACT located behind the distributor.

 

Thanks That is fine I couldnt remember about the crank but i just wanted to confirm there was not supposed to be an air temp sensor or anything going to the air box.

 

Are you sure this hole isn't for the breather filter?