1989 GMC IDLE ISSUES

  • Tiny
  • custom81sg
  • 1989 GMC

Engine Performance problem
1989 Other GMC Models V8 Four Wheel Drive Automatic 125000 miles

I have a 1989 gmc v2500 suburban with a 5.7 tbi.
It initially failed the emissions test in mass so I replaced the egr valve. When I brought the truck for a retest it failed again. The Mechanic suggested I replace the oxygen sensor he told me that this usually fixes the problem. I replaced the sensor and the truck ran beutiful for about 4 hours. That same day the truck stopped idleing and began running like it had a choke stuck. So many suggestions and many frustrating days later I still have a poor idleing truck. I have replaced the temp sensor in the intake, The IAC sensor, tps, map sensor, Spark controll box, cap, rotor, wires, plugs, air filter and most vaccum lines. Im running out of patience and money PLEASE HELP ME!

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Friday, March 14th, 2008 AT 6:08 PM

3 Replies

  • Tiny
  • pear69
  • Member

The problem sounds like a fuel delivery issue. A bad pressure regulator will cause this. Before you go changing this, consider just rebuilding the entire TBI. You can get a complete rebuild kit for a reasonable price. Also, an injector may be leaking. Take the air cleaner off and look at the way the fuel sprays. It should be a fine spray with no dripping. If it drips out of the injector then it could be a bad injector or a bad pressure regulator.

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Saturday, March 15th, 2008 AT 3:14 AM
  • Tiny
  • custom81sg
  • Member

I did rebuilt the tbi as well as put a new diaphram in the regulator. No air leaks in the base gasket or intake manifold it almost seems as if there is not enough air going thru the tbi. When I unplug the pvc right at the tbi the truck wants to run better but still almost stalls

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Saturday, March 15th, 2008 AT 6:36 AM
  • Tiny
  • pear69
  • Member

Have the catalytic converter flow tested.

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Sunday, March 16th, 2008 AT 6:43 PM

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