Truck idles fine with a/c off, and acts ok while driving with a/c on. Just replaced fuel pump and filter a week or so ago after pump just stopped working one day. Throttle body has been replaced because of a faulty wire or somethink like that about a year ago, and truck has no converters
SOURCE: 2000 gmc rough idle
Im not sure if this can help, but my 2000 gmc sierra was idling badly. Replaced Fuel Pressure Regulator and my truck runs like its brand new. My service engine light was also on.
SOURCE: i have a 1994 gmc safari.It seems to have a smooth idle at times
Im not sure if you got it fixed yet! It could possibly be idle air control valve. But here some more suggestions! I had a 94 Safari van 4.3 liter I was working on for about three days and I finally figured out what was wrong with it. It would run fine for a couple minutes and as soon as I hit the gas and let off it would surge, but anyways I ended up changing the distributer, after the fuel pump and filter, mass air flow sensor, egr valve, idle air control valve, map sensor, and ignition module. So that might sove the problem if you were on the same track with it as I was. Hope this helps ya!
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/
SOURCE: My 2003 GMC Sierra Idles Rough And Cut Off
Before replacing the O2 sensors, I would check the fuel pressure. You may also try to have someone pull a trouble code from the powertrain control module to verify why the engine light is on. Do not replace any parts until this is done, otherwise your going to be guessing at the root cause, and it will get expensive with part replacement.
Testimonial: "Trouble code P0101 {Mass Air Flow}and code P0332 Knock Sensor.Thanks i saved a lot money."
SOURCE: 2003 GMC Yukon XL- We have the codes of P0174 and
One of the things to look for is a vacuum leak, especially around the throttle body area. Make sure the throttle body gasket is not rolled and is seated properly. also check the PVC hose for leaks.
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