1991 GMC Sierra runs rich, wont idle

Tiny
BRADLYCT
  • MEMBER
  • 1991 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
My GMC will almost die and then rev up, and miss badly on acceleration. I have tried to troubleshoot it and have not made any progress. It does not bring up any codes, I have changed fuel filter, plugs, wires, rotor, dist cap, o2 sensor, coolant temp sensor, throttle pos sensor, idle speed module, intake manifold gasket, rebuilt throttle body, replaced injectors, and fuel pump. When it runs the intake manifold gets alot of excess fuel sitting in the bottom. I have taken the truck to different shops and they are at a loss. Anything would help, Thanks
Thursday, December 4th, 2008 AT 8:42 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Running rich could be one of the following. Possible causes include a bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.
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Thursday, December 4th, 2008 AT 8:50 PM

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