1993 Chevrolet Silverado • 6 cylinder 2WD Manual • 112,000 miles

Why does my truck cut out under a load?
I have a 1993 chevrolet silverado 4.3 5 speed trans. Under a load taking off or sometimes just crusing and starting an incline on the freeway it starts to buck and cut out and loses power. I have changed the distributor, plugs, plug wires, cap, rotor, and coil. Still does it. Its been in the shop several times and they cant figure it out. Its been on the laptop severl times watching all the sensors. I dont think they know what their doing. The fuel pressure is good they say but they didnt test it under the load. I have heard of something to with the return or something in the fuel pickup causing an instant drop in fuel pressure under a load. Any ideas ill try.
February 23, 2011.

Could be one of the following below -check and test: Oxygen sensors.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note: If it doesn't apply disregard.

Feb 23, 2011.
What is the vacuim switch that operates the egr valve

May 11, 2012.
That's a vacuum port that alows vacuum to get to the egr valve.

May 12, 2012.