1998 Chevy Truck No Power

1998 CHEVROLET TRUCK
220,000 MILES • V8 • 4WD • MANUAL
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BELLTF
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My truck struggles up big hills and has trouble towing. I disconnected the MAF and the engine performed much better. I was able to pull my trailer up hill no problem. I am using 93 octane because it will knock under acceleration if I use 98 or 87. Also, idle is a little rough and when I release the accelerator the rpms do not drop. The truck will continue at the same speed fo a while and then slow down. Sometimes it will not slow down at all an I have to take it out of gear. I have replaced the cap, rotor, plugs, and wires. Thank you for your response.
Jun 13, 2010 at 9:06 AM
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PEAR69
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Test the Throttle Position Sensor (TPS). This sensor is located on the throttle body. It is a potentiometer (3 wire sensor). The voltage changes - up and down - 'smoothly' , as the throttle is opened and closed. This voltage is read by the computer and the fuel delivery is adjusted accordingly. If the TPS is failing the computer will deliver the wrong amount of fuel.
Jun 13, 2010 at 7:08 PM
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BELLTF
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I got 1 volt with throttle closed and 4 volts with throttle open. Looked smooth. The readings did not jump around. My meter will only display 1v increments though.
Jun 13, 2010 at 9:50 PM
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PEAR69
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When the engine is hot, check the throttle body butterfly valve for smooth operation. Sometimes the throttle body shaft wears, and causes the throttle to stick..If this is the case, the entire throttle body must be replaced..
Jun 14, 2010 at 1:31 AM
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BELLTF
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Sorry, I for got to mention that the RPMs only stay high (~1700 rpm) if I release the pedal when the truck is in gear. Throttle works fine when the truck is not moving. Would a sticky throttle affect engine power?
Jun 14, 2010 at 9:36 AM