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I have a 97 GMC Sierra 1500 4

Tiny
BEAV1411
  • MEMBER
  • 1997 GMC SIERRA
  • 96,000 MILES
I have a 97 gmc sierra 1500 4.3L hestitation at idle and sometimes at first acceleration.
i have changed the O2 sensors, plugs wires cap and rotor, coil, checked fuel rail pressure and have done a vacuum test and still nothing. There are no codes and the CEL has never came on.
Any advice would help.
Thanks Dan.
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Friday, November 16th, 2012 AT 7:09 PM

5 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
What is the fuel pressure spec? Do you have the spider fuel system? That type system is known for problems. Cold start idle issues? Runs ok after warm-up?
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Friday, November 16th, 2012 AT 7:57 PM
Tiny
BEAV1411
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  • 3 POSTS
Fuel pressure spec that I was given was 56-60 at startup, idle around 55-56psi with a pound or two drop off at engine shutoff.
As fur the spider fuel system I believe I don't.
Air temperature doesn't matter and engine temp doesn't matter, I have had a no start for two days and after I got it towed to the shop the next morning it started and ran the best it has in a while.
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Friday, November 16th, 2012 AT 9:24 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
You do have the spider fuel system. 60--66 psi, key on engine off. Psi is less with engine running. I'd check codes anyway, I've had inactive codes point me in the right direction. I need more info to go on.
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Saturday, November 17th, 2012 AT 2:44 AM
Tiny
BEAV1411
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  • 3 POSTS
I have check for codes before and I have none. As for me having the spider fuel system how do you know if that is the problem? What tests do I proform? My fuel pressure at key on engine off is 60-61psi. I have just finished running engine and spray brake cleaner around intake and twice I had a poping sound on the left rear side of the intake but I can't get it to do it again. In the area of the intake and the cap. The rpm did not rise so I don't think vacuum leak. Got any more ideas.
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Sunday, November 18th, 2012 AT 5:04 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
This info is for hesitation--sag and stumble, no codes.
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Sunday, November 18th, 2012 AT 6:03 PM

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