1993 Chev 1500 pick up

Is your PU throttle body or port injection?

Remove the idle air valve from the side of the throttle body. Using some carb cleaner, clean the area in the throttle body as well as the module. Remove all the carbon deposits.

Replace it and start the engine. It will run rough for a bit because of the cleaner. Let the engine get warm

Unplug the IAC motor on the side of the throttle body.

Set base idle with the adjusting screw on the side of the throttle body to 400-450 RPM

Shut the engine off

plug the IAC back in and start the engine. Drive it for about 5 miles to reset the computer.

Shut off the engine. Disconnect the neg battery lead for about 15 seconds.

Let the truck idle for a bit and see how the idle settles in.

If this doesn't work you may have to replace the IAC.

NEVER- NEVER adjust the idle screw on the throttle body unless you follow this procedure.

Good luck

Sorry I have been away from my computer for a few days. I was off doing a book signing.

I would check the ignition timing. First locate the brown connector located in and around the harness just above the distributer. With the truck off disconnect the "spout". Set up you timing light start the truck and bump the timing up 2 or 3 degrees. I like to see your engine set about 5 degrees BTDC. The 0 setting makes the engine slug a little. The increase will increse idle about 50-75 RPM.

Shut the engine off, disconnect the battery to clear the check engine light and drive it for a couple of miles and see how the idle RPM settles in.

I have also seen a transmission fluid and filter change increase the idle speed. Also what viscosity oil do you use in the engine?

Let me know