I have a 94 Chevy Cheyenne with 330,000 miles. 4.3 V6. Automatic trans. My problem is the truck starts bucking around 50 to 60mph. Changed out fuel filter, MAP valve, and Throttle position sensor. Engine light comes on and off. When the light comes on sometimes the bucking will stop then again it gets worst. Just wondering, anybody in the Chevy family have any ideas what could be causing my problem? I thought about looking at the overdrive solenoid to be a corrupt.

 

How is your air filter. Mine was dirty and changing the air fuel mixture and making it buck... any codes.