2003 GMC Envoy loses power. I may get 10 feet or 10 miles, but then the Reduced Engine Power light comes on and it's no joke. Lucky to get to 30 mph. Turn the ignition off and back on and I can get another 10 feet or 10 miles before it does it again. Accelerator pedal and sensor were replaced, but still same problem. It's still in the shop now, but it won't act up for them. Figures. Suggestions?

SOURCE: What does reduced engine power light mean

this model has what they call fly by wire.. no accelerator cable. If the computer detects a problem in the thottle system it will not allow the engine to accelerate and will show reduced power and possibly set a check engine light. The dealer usually wants to replace the throttle assembly which is very expensive and usually un nessesary.
I have had a lot of succes with just cleaning the throttle plates real good.

SOURCE: Getting on interstate when increasing

Hello, Check the wiring at the throttle body on the motor that drives the throttle plate. Wires can be broken inside the insulation or bad contact at the connector.