I accidentally drove my Chevy truck in low 3rd gear at 65 mph for about 8 min. or 5 miles. The truck slowly bogged down and I limped back home. Since then, I cannot seem to get things back to normal. Before this happened, I had everything running great. It seems like a fuel problem. I can start the engine but it idles very rough and I can get it up to 3000rpm but after about 30sec, It looses power and decelerates. Had several DTC codes but the one I cannot get rid of is PO300 (random misfire) and even though I replaced the MAF, I still get an occasional PO101 code. I replaced the MAP, MAF and since It has 185000mi, I also replaced the oil pump, timing chain and water pump. I still have same symptoms. And I have reset the computer and cleaned the throttle body. I have not attempted to do anything to the throttle control yet. I have 62psi fuel pressure at the rail and I have tested the fuel regulator and checked for air intake leaks. Can you help? would the transmission solenoids make it run badly in idle? Since I drove it the way I did, I was looking for mechanical problems but I see none.
First thought, intake gasket.
Though the cause of the problem may or may not be the intake manifold gasket I still am leaning toward a vacuum leak of some kind. Since you have a p0300 misfire code it also falls in that category. But lets get you the technical information so we don’t leave anything.
Chevy Code P0300
