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2004 gmc envoy_slt
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2 Posts
Discussion Starter · #1 ·
Hello... I have an 04 GMC Envoy SLT. Its an I6 and just had the transmission rebuilt. It has around 116K miles, and the plugs were changed less than a year ago as well as a professional fuel system cleaning. They cleaned the coil packs but did not change any out.

About 6 months ago, well before the transmission went out I started having Idle problems. It would idle rough all the time, so using the steps someone posted on here I removed the Throttle Body and cleaned it really well with the battery unplugged for at least a half hour. Most of the idle problems went away, it idles great in park and neutral, but now it still idles rough when in drive at a stop. If I put it in neutral the vibration goes away. Then if I put it back in drive and the car shakes and idles rough. Sometimes it shuts off rough, I will turn the key off and it shakes a bit just for a second before it shuts all the way off. Also, when I accelerate from a stop or on the hwy cruising and accelerate fast it is rough and makes a noise that sounds like its coming from the engine, and I can feel a slight knocking in the peddle. Its not a loud noise, but it sounds as if my I6 became a big rig, its almost like a knocking but not, (though to explain the sound) and the knock increases in rate as I press on the gas peddle. What I am thinking is that one of the coil packs is going bad and causing a miss fire, but I am not sure how to test them, or if that is even the problem. Any help would be greatly appreciated. Thanks in advance. :bonk:
 

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2002 chevy trailblazer_ltz
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3,250 Posts
Check for broken motor mount(s) too.
 

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2004 gmc envoy_slt
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2 Posts
Discussion Starter · #5 ·
They used Delco plugs and it was serviced at a well known shop, but I will pull a few and check the gaps. When I called they said they had flushed they fuel system, but I will change the fuel filter because they didn't mention that. I haven't checked the engine mount yet. I did the Throttle body myself so I know its good. I normally always do the work, but it was my dads car at the time. Thanks I'll try these out and get back to y'all :crazy:
 

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2005 chevy trailblazer_lt
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26 Posts
This may not help but...

I replaced a bunch of engine components awhile ago (alternator, fan clutch, tensioner, idle pulley, water pump, thermostat, etc.) and when I took her out for a drive, I had similar shaking problems, rough idle, and I could feel it in the pedal. I popped the hood and tinkered with some things, and it turns out I did not securely mount the fan clutch. It was unbalanced causing it to shake and making my truck howl like a "big rig."

Again, this probably is not the case but it may be worth popping the hood and checking the fan for 2 minutes.
 
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