I have a 1991 GMC Sierra 350 5.7L. It runs really really rough on start up, when the weather is warner it runs better, not good, just better. I have replaced plugs, wire, pick up coil, ignition coil, rotor and fuel filter. I am stumped on this one, i usually am pretty good at working on vehicles, but i am at a loss of ideas. I have heard that it could be your Oil Pressure Sensor, retarding your firing? After i warm it up it will not run that bad but off the jump it does, for example when i take off onto the highway from the access road i have to punch it because if not it will bog down bad and accelerate and a very minimal speed. HELP
Could be the TPI Sensor or it might be a touch out of timing.
Check your electronic spark control module and knock sensor, or your throttle position sensor
I have a 2000 gmc 2500 with the 5.7 motor in it it runs really rough and back fires when you gas it hard... also I have changed the plugs and wires and yes they have been double checked and are on right why would it run so bad??
Check all your vacum lines on you TBI for cracks
SOURCE: 1991 GMC sierra stalls
bad coolant temp sensor,or idle air control valve, and possilbly just low fuel pres.
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