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2000 GMC Sierra 2500:
Sticky Accelerator, Throttle Plate Carbon

Alex Steele
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seen in Truck Trend



I have a 2000 GMC Sierra 2500 4x4 that has a sticky accelerator. When the truck is off, the accelerator pedal depresses smoothly. When the truck is started, the accelerator pedal sticks upon the initial depression, but is fine after that.


I checked the cable at the throttle housing unit and it seems to be working fine. What could be the problem? Any suggestions would help. The truck is also fuel injected.




That "sticking feel" is a common matter on a variety of engines. It's actually the throttle plate itself sticking within the bore of the throttle body assembly. Engine vacuum pulls on the throttle plate and aggravates the "stickiness" while the engine is running.


Not always, but a lot of the time a good cleaning of the carbon build-up on the backside of the throttle plate and inside the throttle bore will fix the problem. Take note that this throttle plate carbon accumulation can also initiate a stalling condition. You can fix it yourself by removing the intake duct work, opening the throttle plate and wiping off the plate and the bore with a shop rag saturated by a cleaning solvent. My favorite, and worth the ride to a GM dealer, is General Motors' Top Engine Cleaner.


On some high-mileage engines the carbon build-up becomes so severe that removal and disassembly of the throttle body assembly is required to get it clean. In case you were wondering, this carbon build-up comes from exhaust gases being mixed with the engine's air/fuel mixture inside the intake manifold, courtesy of the EGR (Exhaust Gas Recirculation) valve. This process actually reduces combustion temperature and emissions output.


The worst case scenario is when the throttle plate has become misaligned and/or has dug a groove into the throttle bore. This is usually the case when cleaning doesn't help and will require replacement of the entire throttle body assembly -- not cheap. Note: do not mess with the set screw on the throttle body. It's preset from the factory and will affect the powertrain control system's ability to control engine idle speed correctly.


Related Topics:  

GMC | Fuel Injection | Engine Maintenance | Stalls
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bud sanders
06 Aug 2012, 13:01
I own 2000 GMC with 361,000 miles on it. Have to clean throttle body once a year, then everything is fine.


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