I have a 1993 Chevy K1500 with 4.3 V6, 4X4, auto transmission and 190,000 miles on the original engine. The truck is running very poorly with loss of power, hesitation, surging, and rough idle, especially between 1000 and 3000 RPM. I have replaced every sensor known to man, checked for vacuum leaks, replaced TBI base gasket, new catalytic converter, compression is 175psi all around, injectors spray a nice cone, fuel pressure is good, New: egr, map sensor, egr solenoid, plugs, wires, coil, ignition module, knock sensor, temperature sensor, cap & rotor, timing is good, I did the timing chain and gears 35,000 miles ago. I have gotten codes 3-2 (EGR) and 3-3 (Manifold Pressure) but both check out OK now. I don't hear any knocking and although the ending runs like crap throughout the whole RPM range it used to run quite well at higher RPMS even when it ran bad at low RPMS. I am totally lost and I would just through a rebuilt engine in but I'm afraid the problem is a peripheral component that would show up even with a new engine. If anyone has any suggestions or similar experiences I would really appreciate hearing about them.

Thanks,

Dain LaRoche

double check the timing and unhook & plug vacuum hose to egr. did you hook up a vacuum gage? maybe the brake booster is leaking

Thanks, I thought of that too. Yesterday we hooked up a scan tool and checked out the MAP sensor circuit. Using a vacuum pump we put 15" of vacuum to it and the voltage didn't change. It was a brand new MAP sensor but we tried another one just to see and we got the same thing. We checked the wiring harness for a short but were unable to find one. The next step is to replace the computer. Because the computer thought there was no vacuum it responded like the pedal was all the way to the floor and was dumping gas into the manifold causing an overly rich mixture. This explains why it ran well on the top end but poorly at lower RPMs.

Try this, and it won't cost any money. Take the plug wires out of their seperators and position them so that they are as far away from each other as possible. Then try running engine. I had TONS of troubles with wires, even brand new ones.

Hope this helps.

Worn cam lobes? fuel filter?