Engine Performance problem
1992 Chevy Truck V8 Two Wheel Drive Automatic 231000 miles
I just replaced the fuel pump in my 1992 Chevy c1500. The vehicle would idle fine but would stumble under acceleration like it was running out of gas. So I checked the fuel pressure at the TBI unit, it was 5 psi. So I changed the fuel filter, that increased the pressure to almost 8 psi, but the it still sounded like it was running out of fuel. I removed the bed, replaced the fuel pump, strainer and inspected the harness inside the tank. Harness looked very good, as if it had been replaced before. Once finished I started the vehicle, it still stumbles under acceleration like its running out of gas. I checked the voltage at the connector outside the tank, it was 8.79 volts, key on engine off. When driving it it very sluggish and even tried to spit back through the TBI unit a little under hard acceleration. The engine idles perfect and revs up fine as long as your not driving it or have it under a load. What else should be checked?
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)
Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include: Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires