1995 Chevy Silverado 1995 C1500 350 5-SPD fast idle problem

Tiny
HSV_MIKEJ
  • MEMBER
  • 1995 CHEVROLET SILVERADO
  • V8
  • 2WD
  • MANUAL
  • 12,100 MILES
My 1995 C1500 5.7 TBI 5-spd has a problem. When I first crank it, I will see an service engine light for about 30 seconds then it goes out. The truck will idle about 1000 RPM, until I start to drive, then the idle will hold at about 1900 RPM. I've looked for loose vaccuum lines but could not find any loose ones. I do have an aftermarket chip installed, but the problem is there even with the stock chip.


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Wednesday, October 22nd, 2008 AT 12:53 PM

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Tiny
RASMATAZ
  • MEMBER
Hi hsv_mikej and welcome to 2carpros

1995 Chevy Silverado 1995 C1500 350 5-spd fast idle problem

Scan the computer for DTC's

Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor/valve stuck in the extended (high idle speed) position/throttle position sensor. Also the throttle plate could be binding in its bore and kinked accelerator cable, coolant temperature sensor might not be operating properly misleading the computer that the engine is still cold and computer throwing fuel at it raising the idle speed.
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Wednesday, October 22nd, 2008 AT 3:21 PM

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