1999 GMC NO POWER WHEN COLD

  • Tiny
  • paylone20
  • 1999 GMC

Engine Mechanical problem
1999 Other GMC Models V8 Four Wheel Drive Automatic 136000 miles

when engine is cold it runs real rough. No power back fires. When warm runs better but not full power. I have changed mass air senser, egr valve throttle position senser plugs wires, checked pressure in cats and fuel pressure is good, and I changed fuel filter can u please help

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Sunday, September 27th, 2009 AT 3:47 PM

6 Replies

  • Tiny
  • Docfixit
  • Expert
  • 18,993 posts

Hi
Have you checked for codes? What is engine compression? Assume all the parts replaced made no difference? Any backfiring? Loss of fuel milage?
Let me know
Thanks for donate

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Sunday, September 27th, 2009 AT 4:13 PM
  • Tiny
  • paylone20
  • Member

Yes I have checked for codes no codes. And have had it hooked to computer when it is doing it. Could u give me anything else.

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Sunday, September 27th, 2009 AT 4:26 PM
  • Tiny
  • Docfixit
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  • 18,993 posts

Would you answer all questions please need all info I can get to help

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Sunday, September 27th, 2009 AT 4:37 PM
  • Tiny
  • paylone20
  • Member

Yes I have had a compression test done on it. What other info do u need to no. I have tried everything that I could think of please help

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Sunday, September 27th, 2009 AT 10:45 PM
  • Tiny
  • paylone20
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Yes it also backfires and fuel milege is below par for sure.

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Sunday, September 27th, 2009 AT 11:44 PM
  • Tiny
  • Docfixit
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  • 18,993 posts

Ohm check two sensors the Engine coolant temp and Air intake temp sensor. The ECT is next to thermostat and IAT in air intake. They should ohm out at 86 degrees- 2238 ohms, 104 degrees-1459 ohms, 212 degrees- 177ohms.

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Monday, September 28th, 2009 AT 8:52 AM

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