Can someone explain to be how the idle and throttle work together in my 351w engine. Immediately upon starting the truck either hot or cold it wants to die, however, if i push the rpms to 1.5k for a few second and then release and its ok, like a jumping misfiring feel.

DONE: I've replace all cap rotor wires plugs fuel filter, had dist adjusted correctly. Removed breather from Air Filter box to eliminate oil in the Air Filter.

NEAR FUTURE: Coil, Brakes and Rotors, Teflon Engine Treatment.

Recently I had a vacume hose unplugged that was causing me to dye at stoplights.

Quesiton: I have two options, my Dad a chemical engineer says to put thicker oil to reduce blow by. My mechanic says to use an engine restore type treatment to get what I can out of the engine. Who's right?

 

Sounds like you may have IAC difficulties. You might try removing it and cleaning the valve out. They get gunmmed up with carbon and crud periodically. During warm-up and at idle the IAC controls the amount of air bypassing the throttle plates to maintain idle RPM's. The "jumping misfiring feel" sounds like it may just be sticky and trying to open. If you disconnect it (three wire connector) the truck should fall on its face and die shortly even after the engine is at op. temp. If you do disconnect it you will have to clear the computer codes once you reconnect it. Whatever you do, DON'T adjust the idle stop screw in the top of the throttle body. Its not an adjuster merely a stop to keep the throttle plates from jamming in the bores.

The IAC is attached to the left (driver's) side of the throttle body via a couple of bolts. Once removed it can be cleaned with carb and choke cleaner but take care not to get too much in the soleniod portion of the component. Make sure the gasket is ok or just replace it.

If the IAC fails completely, you will need the Calibration Code from the driver's door jamb when ordering a replacement.

 

Where can I find a diagram for the IAC or instructions? What does IAC Stand for?

Thanx!!!

 

IAC = Idle Air Control solenoid and valve. Its just a solenoid that controls an air valve. There is one three-wire connector that controls it. It takes its cue from the ECM (engine control module). There is no adjustment for it. It either works, sticks, or doesn't work at all. The Haynes manual lists a method for checking it that is rather lengthy.