i have a 1989 f150 4x4 with the 5.0 . this truck has drove me insane it is only running on 3 cylinders i have changed ecu injectors saprk plug wires checked compression gutted cats checked cams what the hell can this be?????

 

Sounds like it could be the ignition control module. On my 89 straight six it is mounted to the distributor housing. The heat there causes them to fail. Later models went fender mount. I believe the 302 also has a distributor mounted unit. They carry them in stock at autozone, I forget the price.

 

My '93 302 is on the fender well. But that was the next gen.

 

pull the plugs and see if its fuel or spark that is not happening. Maybe stator under the rotor. Tke a sniff of your oil if it smells like gas its most likely spark. Did you check the codes. If it was a fuel or sensor problem it should come up. I thought these trucks had the tfi box right next to the drivers side hood hinge.

 

The tfi, or icm, on the 89 model is distributor mounted. They started doing a remote location on it a few years later, I don't remember when it started. But I agree with checking codes. Hopefully he already has though, as thats a lot of money to throw into parts before running a diagnostic first.

 

Given what you've already replaced, I suggest replacing your wires and distrib. cap, seafoaming (dead horse sufficiently beaten), some lucas injector cleaner (even though you already replaced your injections, might be worth it unless you've changed the lines), and run your codes. Keep us posted and don't give up on the truck!