I'm stumped again... a month ago I was headed through the mountains and my truck (93 x-cab 4x4/22re) started missing occasionally. by the time I got home, it was much worse, and over the next few days it got to where I can hardly get out of the tiny valley I live in because it won't climb hills. it runs like a champ when it's cold - no noises, no missing, lots of power. as soon as it gets 'hot' - fully warmed up - it starts to miss a bit under part-throttle acceleration, and then it starts to knock really, really bad if I put the pedal on the floor. and miss, and knock, under part throttle. low rpm's are worse than high. it won't throw a code, though. [I]nothing[I]. I replaced the plugs and wires (my plugs were badly deposited, she burns a fair bit of oil) I tested the ignition coil by swapping in the one from my other truck, and same for the AFM. checked the valve clearance, compression tested at 160-175psi, the fuel filter is only 10k old, and I haven't tested the fuel pressure but it is definitely flowing plenty.

I just can't figure out how it could be running so terribly and not be throwing a CEL. anyone have ideas?

 

oh yeah. to describe what it's doing, I would make my first guess that it's overheating really bad - that's how it acts. but I checked the thermostat and it's working properly, the dash guage reads right where it always has, and it doesn't seem overly hot when I work on it.

 

Sounds to me like the EGR valve might be sticking open. That wouldn't necessarily throw a code. It would just cause a vacuum leak at low rpms and make your engine act like your describing.

 

 

Hmmmmm....anybody home?

I could be wrong you know? Or was I right?