Random Misfire After Hard Acceleration

[GNabors]

I have a '97 Z71 w/ vortec engine. When climbing a hill, especially with a load, I have a lost of power, then when I top the hill and begin easing off the accelerator, it begins missing so badly it almost feels like something suddenly became seriously unbalanced in the engine. The misfire gradually goes away over a 20-30 seconds. The only engine code that shows up is random misfire. I've tried a new fuel pump, dist cap, rotor and wires, to no avail. The pickup has 230,000 miles, yeah, I now, a lot... but other than that, it runs great. Any ideas anyone?

[maxwedge]

Welcome to AF, this is a typical symptom of the valves hanging up in the valve guides from excess carbon build up, this was exaggerated by the original machining of the guides not providing sufficient clerarance, there are other possibiilites here but the symptoms match the condition. A professional carbon treatment done by a GM dealer would be the cheapest way to attack this, short of pulling the heads. Just to be sure, have the fuel pressure tested first, look for 60-65 psi.

[j cAT]

Originally Posted by GNabors

I have a '97 Z71 w/ vortec engine. When climbing a hill, especially with a load, I have a lost of power, then when I top the hill and begin easing off the accelerator, it begins missing so badly it almost feels like something suddenly became seriously unbalanced in the engine. The misfire gradually goes away over a 20-30 seconds. The only engine code that shows up is random misfire. I've tried a new fuel pump, dist cap, rotor and wires, to no avail. The pickup has 230,000 miles, yeah, I now, a lot... but other than that, it runs great. Any ideas anyone?

compression check....may need valve job...

[GNabors]

Thanks guys... I'll look into those suggestions.