Question about 1999 GMC Sierra
6 litre 4x4-
When started, it idles low (500rpm) in park.
When warm (at stoplights) it will sputter and stall.
In drive over 60km/h when you push pedal it revs, but no go-have to put it in 3rd.
Code reader said P0122, so changed the TPS, & a blown 40amp fuse, cleaned battery terminals, changed plugs and wires, fuel filter, IAC, cleaned the throttle body, MAF, and EGR. Checked for a vacuum leak, and voltage to TPS. Did idle learn, checked fuel pressure reg, and did compression test.
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Posted on Jan 02, 2017
had same problem i would check the Idel Air Valve and also check all of your vaccum hose lines makeing sure there are no cracks or splits in rubber connectors if there is repair immediatelt because over time they start to dammage the internal parts fo the engine and if youve replace tps mass air etc. sounds like a vaccum hose problem
Posted on Feb 10, 2009
On the plus side, when you are finished, you will have a new control system! On the negative side, you just spent more money on parts than if you'd have just taken it to a dealer! I hope you tested those components and determined they have failed. Any codes?
Seems like the only thing you missed is the coil and the temp sending unit (just for laughs, unplug it and see if it stalls out at the same time), or possibly a security system malfunction. Get a decent volt/ohmeter and a vehicle specific manual such as chiltons or haynes. Do some testing, hot and cold and compare your results.You need to determine what is shutting down (fuel, spark or both) Once you develop a "picture" regarding what is happening, you will be more able to find a solution. I can't give you a "fix" on this one only because to properly identify the problem, I'd need to do the same testing I suggested.
Posted on Sep 03, 2009
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.
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Here is a link that my help you in the future. http://www.troublecodes.net/GM/
Posted on Mar 16, 2010
Unfortunetly....these spider injectors and fuel pumps can have very similar symptoms when failing. What I do know is I work on this motor more than any other motor in my shop. Very common with fuel problems...and I can comfortably tell you that they updated the injector kits on these car for a reason. The original model is junk. I have done these on just about every one of my cutomers vehicles over 150,000 miles. However, I am not going to tell you that is your problem....but it sounds fuel related. Did/does your vehicle skip? Leaking injectors will usually cause a skip due to shortage of fuel to that cylinder. I also have a computer that allows me to monitor the firing of each cylinder, and do an injector kill test. This is what I would do first. Unfortunetly, sounds like you can't so start with this: Clean your throttle body. The pintle that the IAC motor pushes in and out goes into a small port. Spray that port out with carb clean. Get a fine wire brush and get that throttle body clean and shinny. That pintle can easily stick on existing carbon in that port...new part or not. Check for vacuum leaking with carb clean...spray it around the intake and vacuum hoses...see if any particular spot changes how it runs when you spray it. Do you have a vacuum gauge? what is manifold vacuum? Since you are in the intake...make sure your puddled fuel is not due to pulling the main lines off the the injector assembly. After intake is off. hook fuel lines and harnes back up to injector assembly. key up (no start) vehicle...this pressurizes fuel system. look for leaking. The fuel pressure regulator is built on to the side of that assembly....its the round diaphragm with the tube coming out of it. If it leaks fuel out...that may be your problem. And you can replace that without doing the whole injector kit...fairly cheap. If not fixed....what is your fuel pressure. You need to have 60-64 PSI at key up. Try the carbon build up and intake test first...both quick, easy, and cheap. If this is not your issues...its sounds fuel related....just want to confirm that you don have a misfire/skip. That could change diagnosis quite a bit. Keep me posted....more than happy to help. By the way....I own all GM's too...lol...haven't learned my lesson yet
Posted on Nov 14, 2010
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This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control
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