Ok Looking for some Chevy Yoda wisdom here. My truck has a 7.4 liter motor with 90 K miles. Been a very reliable truck. It recently developed a symptom similar to a mis-fire. I thought it was a fuel filter issue to start, replaced it, truck ran great (was cool not cold) for a bit then repeated the behavior (after truck warmed up). Towed it to the shop,( He had to warm it up for it to repeat the behavior) Tech said the code was suggesting a random mis-fire. Since the truck had not been tuned up since I have had it (18K miles), he suggested a tune up. after a meticulous replacment of wires, plugs, rotor, rotor cap and air filter it ran great (was cold) then repeated behavior (after it warmed up). I continued driving to get it home when all the sudden it started running fine again. Drove it for about another 25 miles with no problem. Parked it for two hours, came back, started it up and it ran fine, once warmed up it repeated the behavior then after driving it for a while behaving poorlly it cleared up and ran fine. WTF is going on here. anyone with some insight that can help?

 

welcome from south carolina