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2005 GMC Sierra 1500 Base Reg Cab 119.0 WB Work Truck

2005 GMC Sierra 1500
Trim Info:
Rear Wheel Drive, Reg Cab 6.5' Wideside
16 mpg city / 22 mpg hwy
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February 7, 2012, 12:02 pm

AutomotiveForums M
 

Question: rough idel

the truck stats and idels fine but taking off and letting off the throughtle the rpm flux even moore once the temp gets to normal operating temprature tps came back good rplaced the fuel filter, fuel screen, still not fixed


February 9, 2012, 8:05 pm

Elizabeth K
Expert Mechanic

If it's mainly a problem at idle when the engine is warmed up, the first thing to look for is a vacuum leak. Here is some more information on that:
http://www.aa1car.com/library/vacleak.htm


0/1 users found this helpful.

February 15, 2012, 7:51 pm

AutomotiveForums M
 

not vacuum its when taking off and first letting off throttle it will level off and idel fine.runsfine if in throttle or running hwy speeds theres no back fire or check eng light or code. it appears to be getting fuel it sounds like well if you put a big lop cam in al most but a cylenders are firing.


0/0 users found this helpful.

February 15, 2012, 8:29 pm

Elizabeth K
Expert Mechanic

Clean the throttle body/butterfly plate. The ECM uses a the MAP (manifold absolute pressure) sensor and TPS to decide pulse width for the injectors, so engine vacuum is still an issue. Best to check the MAP sensor outputs, as well.

How did you test the TPS? Unless you checked the voltage sweep using an oscilloscope, you could be missing a glitch in the resistor. Checking closed and WOT using a voltmeter or ohmmeter is not sufficient.

Are there any problems accelerating at other speeds? How does it handle hard acceleration?


1/1 users found this helpful.

February 17, 2012, 7:07 am

AutomotiveForums M
 

it handle hard accel wel slight lack at maby fraction of second. know truck died and wont start. it acks like its starving.


0/0 users found this helpful.

February 17, 2012, 4:45 pm

Elizabeth K
Expert Mechanic

Well, that makes troubleshooting easier. Here's an article on the steps to take:
http://www.2carpros.com/articles/car-cranks-but-wont-start


0/0 users found this helpful.

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