2002 GMC envoy slt 4.2 v6 My question is.. I recently changed the water pump on my wife's envoy. After replacing it the car idles low and high, low and high constantly. No normal idle like before. I however, did not replace the fan clutch. My question is... would me not changing the fan clutch be causing the idling problems?

The oil pressure drop indicates more problems.

Oil pressure drops to zero at idle on 2002 GMC Envoy after ...

www.fixya.com/cars/t7880379-oil_pressure_drops_zero_idle_2002_gmc Jan 18, 2011 - You could have three possable problems that I can think of. 1) Your oilviscosity is too low and you need to change it to a higher level. A 5w/30 .

It could be an electrical problem or a mechanical problem in transmission or transfer case. does it shift into 4 wheel high okay

This is normal. All vehicles idle high at start up to get the engine to operating temperature. This is known as open loop. The computer ignores signals from O2 sensors to keep your engine running safely. Once it has warmed up, it will enter closed loop, and you will see a decrease in idle.

The pressure regulator in the oil pump may not be working, the idle speed may be too low and there may be a lot of wear on internal engine parts lowering oil pressure

Well, the problem is that I dont know the reason, you should investigate. There could be issues with lamps (must get new) or electricity problems (must head to auto-service)

Shotgunning this problem by replacing random parts will only cost you extra money. You need to have a technician diagnose the problem using a high-end scan tool to read the data that the computer is collecting. Also, the fuel pressure needs to be checked.

Fix your car right away by clicking the link I attached
GMC Envoy 2002 to 2009 Service Workshop Repair manual

This could be a bad key. Expensive but if necassary to replace to check on the symptom of the car since no codes are being thrown. I would also say check your Idle Air Control valve and your EGR valve to make sure they are working proplery

how to remove a bose cd/radio from dash of a GMC envoy slt cd's are stuck inside

I ran into this concern with my 2002 and my wife ran into the almost identical problem with her 2003. this may sound silly,, but it was the clutch fan. Extreme loss of power from time to time came first. Then a roar of the what seemed like the engine when stopping. Actually cut off after it started to roar at highway speeds, and had absolutely no excelleration from time to time. Sometimes all of the symptoms completely went away. After taking mine to the dealer several times, finally they got it right and replaced the fan clutch. When my wifes 2003 SLt started doing the exact same thing as my 2002 had done, we both knew what the problem was, and the dealer did a quick fix. $600.00. Perhaps this should have been a recall feature, but never was. Everyone that I know that has an envoy, somewhere around the 72,000 and 103,000 mile mark has had this problem and have had to have the clutch fan replaced. It may sound like the vehicle is going to have to be junked,, but that is all it needs.