1993 Chevrolet C2500 Suburban Silverado 8 Cyl 7.4L
Engine fluctuates while driving
vehicle warm outside temps low
Your engine fluctuates because your air filter is maybe excessively blocked and the combustion was not supplied by proper air for combustion; or your throttle position sensor is failing giving wrong inputs to ECU. Also the fuel system might be clogged or contaminated causing the engine fluctuates (clogged fuel injectors, blocked fuel filter, contamination in the fuel tank). Check also for fuel pressure; your fuel pump could be failing.