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2002 gmc envoy_slt
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Discussion Starter #1 (Edited)
I have an '02 Envoy that has been giving me fits. A little history, a few years ago it started doing what I would call wheezing. Under acceleration, instead of a low smooth rumble, the engine would sound like it was under a much higher load (RPM's normal) louder and more of a high-pitched whine. Acceleration was very sluggish, it didn't seem to want to rev up to anything above 3K rpm. In the beginning, this only happened when the engine was cold, and would gradually go away as the engine was pushed just a bit, like by the time I got to the end of my street.

The issue progressed and the same behavior began to come and go at random times during a trip and stay for longer and longer periods of time. Then it was accompanied by the engine not starting if it was warm. When this happened, the only way to start it was in "clear flood" mode (cranking with pedal depressed).

I took it to a couple of different shops, and they said it was fuel injectors. Over the months, they performed several different fuel injector services, but it didn't help whatsoever.

Finally, I noticed the temperature guage had begun to wobble and I told the mechanic about that. He decided to try the coolant temp sensor. This seemed to fix the problem. He said that the engine thought it was cold even when it wasn't and was engaging the automatic choke.

Since then I had a different issue with a CEL and slow acceleration and bucking. This one I diagnosed with help from the forum as plugged CAT (which could have resulted from the engine running rich all the time). Replaced the CAT and O2 sensors and that problem was solved as well.

Now... The wheezing is back along with a CEL. It has been less than a year since the coolant temp sensor was replaced. I suppose that the part could have gone bad in that short of a time, but before I start throwing money and parts at it I wanted to see if anyone else had had the same experience. I haven't pulled the code yet because the car is in the body shop for a fender ding, but I should get it back today and pull the code then.

From another thread I think I need to replace the motor mounts (idle vibration) and I plan to replace plugs and clean TB and MAF as a preventative measure. Any reason to check the CPAS as well? I'm a novice mechanic and my experience is limited to brakes and replacing the CAT and O2 sensors, but I'm willing to try anything (although I typically shy away from things that involve any type of fluid). FYI, the truck has 150k miles.

I know it's a novel, I tend to be long winded. If you made it this far, thanks!
 

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2002 gmc envoy_slt
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3 Posts
Discussion Starter #2
Could be the fan clutch?

After browsing the forums some more, I think it could be the fan clutch. Does a bad fan clutch usually also show up with loss of power in addition to sounding like an F16?

I read that there is a revised version that requires a programming update, is this something the dealer will do for free?
 

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2003 trailblazer_lt
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84 Posts
Yes, there is a significant loss of power with a failed fan clutch.

I've put a new fan clutch on both of our TBs without getting the PCM update from the dealer. It's not required, but it is supposed to improve AC cooling immediately after startup and at idle. I haven't had any problems with AC cooling in either of those situations without it, though.

It's definitely not a free update; others have posted that it costs ~$100.
 

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2002 gmc envoy_slt
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3 Posts
Discussion Starter #4
Ok, got the car back and got the code pulled, P1484. I believe this is fan speed issue and thus, caused by the fan clutch. I've got 150k miles and I've never had it replaced that I can remember and with as common as this problem seems I'm going to go ahead and order one.

Good time to do a water pump as well or should I just leave well enough alone? Don't remember ever replacing that either. And I'll probably have the reflash done at the dealer as well.
 
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