Hi im new here, i've had some issues lately with my truck. It is a 1989 f250 with a replacement 302 and automatic trans with about 75,000 miles. Lately its been having an issue where when im stopped at a light its idle will start loping to the point where it almost dies and i have to tap the gas to keep it going, along with that at mid range rpms (1800-2300) it seems sluggish and the engine again revs up and down. if i stomp on the gas during this it might hesitate for a second but will jump to high rpms just fine. Typically It does not do any of this till the truck is hot. So far i've tested my tps sensor, gone through and checked my fuel system, and replaced my iac with no results. Im thinking its possibly the icm on the distributor or my ignition coil?? Any help would be great thanks!

 

Have you pulled codes? Inspect all vacuum lines if you haven't.

 

I pulled codes with engine not running and it came back systems ok and i checked for vacuum leaks the other day, i was unable to find any

 

The next things to look at are the map sensor and the ECU. Not sure how to test a map but pull the computer and open it to inspect for burnt capacitors or other damage to the board.

 

I agree, but would check the fuel pressure reg before I started jacking with the ecu. Also might want to try plugging all the vacuum lines except MAP and FPR and see what it does. If it has the metal vacuum coffee cans they rust on the side seam under the bracket.