My 2007 gmc sierra 5.3 with afm idles rough and shakes the whole truck. it has 37,000 miles on it.it runs great otherwise but this is very annoying. it feels like its got a miss but no codes show up.
SOURCE: 1985 gmc sierra shakes
Sounds to me to be a timming issue like maybe retarted, also chk. to see if the wire is pluged in by dist, the wire that you have to unplug when your going to time it, i can't remember what its called. There is only 2 things on this truck thats controled by the computer is spark and fuel, if that wire is unpluged by dist. it will run like that, unless someone has changed it back to the old style dist. and carb. if thats the case loosen dist. and move it a little and see if it dosent run better, clockwise advance, counter clockwise is retarded.
SOURCE: 2000 gmc starts but then idles rough then dies
I had to replace the mass air flow sensor. $ 150. the engine would shut off when driving too.changed fuel filter only worked for a day. The sensor is just after air filter.
SOURCE: 2004 GMC Sierra 4dr truck. the fan does not work
The switch or the wire harness at the blower motor has gone bad. The highest setting 5 has no resistor, so the blower runs on high but the high current flow ends up burning up the switch's contact on that setting or the resistor wire harness at the blower motor has gone bad. Common would be the switch it self, if the switch is good. Then it's going to be the wire leads at the speed resistor by the blower motor under the glove box by the passenger leg compartment. Keep me posted, be glad to help you get your Sierra running 100% again soon.
SOURCE: 95 GMC Sierra 4x4 350 5.7 rough idle problem
It sounds like a MAP sensor going bad. MAP is short for manifold absolute pressure sensor, it senses the manifold pressure and applies the right amount of gas with the right amount of ignition timing so the car runs and performs well if this does not work properly. It throws off the whole loop cycle for the computer, which in turn makes it run badly and get poor fuel economy. It can causes the engine to have a lack of power, combined with a loss of fuel economy. Poor take offs and sometimes an occasional stalling may occur if the MAP sensor is faulty and sending the wrong signals to the ECM.
Hope this helps and thank you for using Fixya.
Here is a link that my help you in the future.
http://www.troublecodes.net/GM/
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