1990 gmc sierra k1500 5.7 350

Asked by Feb 04, 2017 at 07:34 PM about the 1990 GMC Sierra 1500 K1500 4WD Standard Cab SB

Question type: Maintenance & Repair

My 1990 gmc sierra k1500 5.7 350 will crank and
idle great and Rev fine and you can put it in gear
and drive it somewhat fine but occasionally it
sputters and cuts off and when you mat the gas
pedal to the floor it tries to die out and I have
already replaced the egr, iac, distributor, rotor head,
spark plugs and spark plug wires, map sensor,
alternator, and I have cleaned the throttle body and
put all new gaskets in and I have checked it over
and over for vacuum leaks but the problem still
continues, any ideas of what it could be

1 Answer

Sounds like you might have a fuel issue. Check the pressure at the throttle body if possible. I use a 3/8" brass compression union with the middle section tapped to 1/16" pipe thread. You install this by cutting the line near the Throttle body. You can bush the 1/16 pipe thread up to 1/8" or 1/4" to hook up a gauge. Harbor Freight sells an inexpensive test gauge set. The factory TB has it's pressure set so you or I can't adjust it. But if you had it apart, you can see where the adjusting screw is and then check/adjust it once you get your test gauge hooked up. 12 psi if I remember correctly. Hope this helps. Pat

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