Hello, I have a 1993 GMC Sierra 1500 5.7 v8. only in cool to cold temps the eng. acts like it wants to choke out and die.

Asked by Dec 12, 2015 at 04:52 PM about the 1993 GMC Sierra 1500 C1500 SLE Extended Cab SB

Question type: General

After it warms up it runs better but acts up at times.  in the summer or temps 60 degrees or higher it runs great.  I have changed the fuel filter, spark plugs, cap and rotor.  any ideas why this only happens in cooler weather? Thanks Devon

1 Answer

69,315

Hi Devon, sounds like good old fashioned throttle plate icing. The throttle plate area must be kept warm to avoid ice forming on the throttle plates in cool/cold damp weather. Check your air cleaner assembly and be sure the damper inside the snorkel is working. On a cold start up it should be closed to outside air and pulling air from the hose on the bottom of the snorkel that hooks up to the exhaust manifold area at the other end. If you have a heat riser system check the exhaust manifold heat riser valve. Possibly referred to as an EFE (Early Fuel Evaporation) valve. This valve will have a vacuum hose hooked up to it and is on the right (passenger's side) exhaust manifold back by the firewall. It's job is to direct hot exhaust gasses up under the throttle body area. Sometimes the passage in the intake manifold (exhaust crossover passage) will get clogged with carbon and need to be cleaned out. HTH. -Jim

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