Question about 2003 GMC Yukon XL

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Have a 2003 Gmc Yukon Xl 2500 6.0. When you first start it, the idle is low then high repeatedly. When you take off it sputters and will be ok until its warmed up. We have replaced the battery, spark plugs and wires. This summer really didnt knotice this problem again, but colder temps in the morning the issue is back. The fuel pump went out about 2 years ago. We never let the gas get below 1/4 tank. One time a mechanic said the mass air flow sens was dirty, we cleaned it, reset the code and seemed ok for a few days. Anyone have the same issues?? Thanks

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I suspect the idle solonoid and/or the automatic choke Idle somonoid plays havoc when cold and you have to keep playing with the revs to keep it running. Even though you had cleaned the mas airflow sensor it still may be faulty. I would take it to Orielys or Autozone and ask them to read the codes for you {no charge} this will eliminate the guess work, good luck

Posted on Oct 21, 2013


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Posted on Jan 02, 2017


SOURCE: 1999 GMC Suburban 2500. 454 engine

sounds like fuel pump pressure. I had the same thing happen to me in a Lincoln mark VII and the electrical connection was shorting out in the fuel pump. I changed the fuel pump..Returned under warranty) put the new one on with filter and had no problem with it.

Posted on Oct 10, 2008

  • 114 Answers

SOURCE: 2002 gmc yukon, rich fuel code, low fuel pressure @40

you may have two oxugen sensors on your yukon. if so the oxygen sensor that controls that bank may be bad. from what you mentioned in your complaint, it sounds like it is the oxygen sensor.

Posted on Dec 24, 2008

  • 1 Answer

SOURCE: 2002 GMC Yukon, erratic idle(hi-low) when cold. 125K miles.

i now for a fact that it is the egr valve . carbon balls in side you have to take it of and clean them out

Posted on Apr 18, 2009

  • 43 Answers

SOURCE: 2003 gmc yukon denali xl starts but gas not

if your engine starts up and dies right away the you probably have a fuel pump problem and the service ride control mean that your air ride compressor has gone bad just turn your key to the on position and wait about 30 seconds you will here buzzing from the left rear wheel area if the compressor is working

Posted on Jul 19, 2009

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SOURCE: Hi I have a 98 gmc sierra 1500 with 5.7 vortec,

It's hard to find these small leaks. If you have a vacuum pump, there are a few tests you can run on the components of the system. See below.


Vapor Canister
See Figure 1

  1. Apply a length of hose to the lower tube of the purge valve assembly and attempt to blow air through it. There should be little or no air should passing into the canister.

If the canister is equipped with a constant purge hole, a small amount of air will pass into the canister.
  1. Using a hand-held vacuum pump, apply a vacuum of 15 in. Hg (51 kPa) to the control vacuum (upper) tube. If the vacuum does not hold for at least 20 seconds, the diaphragm is leaking. Replace the canister.
  2. If the diaphragm holds vacuum, attempt to blow air through the hose connected to the PCV tube while vacuum is still being applied. An increase of air should be observed. If no increase is noted, the canister must be replaced.

Fig. Fig. 1: Cross-section of the vapor canister

Fuel Tank Pressure Control Valve

  1. Attach a length of hose to the tank side of the valve assembly and try to blow air through it. Little or no air should pass into the canister.
  2. Using a hand-held vacuum pump, apply vacuum equivalent to 15 in. Hg (51 kPa) to the control vacuum tube. If the diaphragm does not hold vacuum, the diaphragm is leaking. Replace the valve.
  3. If the diaphragm holds vacuum, attempt to blow air through the hose connected to the valve while vacuum is still being applied. Air should pass. If no air is noted, the valve must be replaced.

Thermostatic Vacuum Switch
  1. With engine temperature below 100°F (38°C), apply vacuum to the manifold side of the switch. The switch should hold vacuum.
  2. Start and continue to run the engine until the engine temperature increases above 122°F (50°C). The vacuum should drop off.
  3. Replace the switch if it fails either test.

purge valve location:


EVAP vacuum switch pic:


EVAP system diagram:

Posted on Nov 20, 2010

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the earlier GM trucks had a problem with the a/c systems
Compressors are junk, but this will usually break the a/c belt, and make a horrible noise right before that.
the pressure you have listed is not much help, there is a high and low side pressure. If they are both the same, then the compressor is not on or is not pumping (broke). The early yukons/suburbans/tahoes also had a problem with the a/c cycling switch. If yours has a brown band, replace it.

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Another thing you may want to look at is of course a leak in the system, make sure its fully charged, and check the fan clutch.

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