Need help. Didnt drive my '95 z71 with 5.7 L for a few wks, It was fine the last time I drove it. The next time I did it ran like crap and has since. It hesitates and stumbles and bucks on acceleration under load. If I rev the throttle at idle, I can tell a slight hesitation there too. Its undriveable like this. Changed fuel filter even though I didnt really think it would be culprit. It had no effect. Changes plugs, no effect. compression check looked OK at ~165-170 psi for all cyls by my guage. The engine service light is working, but has not come on to signal any codes . I filled tank with new gas, no change either. checked PCV, clear and clean. what could cause this? Bad fuel pressure or faulty regulator? Or ignition problem?

Check the egr valve and make sure that is not stuck open a little and if that is fine I would check the ignition coil and pick-up coil.

I just bought an 89 that is doing the same thing. So if you figure it out let me know.

Hey MBB , in the previous reply I said my truck was doing the same thing. I checked my timing and it was way off. Distributor clamp was loose. Runs much better now.

I bought the truck running bad. Lucky me it cost nothing to fix.

replace distributor cap and rotor ...no improvement. Put some B12 chemtool in gas tank, voila. Problem gone within a few miles. Looks like must have been sticking injector. Since Ive done the rest of the tuneup timing is next anyway.