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2005 gmc envoy_sle_xl
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Discussion Starter #1
I have a 2005 envoy xl 4.2 that seems to shake when I turn it off. It has been doing this for a while but I just assumed it was the motor mounts. I just replaced the motor mounts this weekend which took care of the vibration but it still shakes when you turn it off. I still need to clean the throttle body, could that be part of the issue?
 

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2006 chevy trailblazer_lt_ext
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198 Posts
Hmm... that's a tough one to offer any assistance on. Is it shaking as if the engine is struggling to stop running?

My brain is going towards EVAP or fuel injector leak in this scenario... but need more info.
 

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2004 chevy trailblazer_ls_ext
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148 Posts
Did you take a look at the transmission mount while you were under there? It's possible that worn motor mounts transmitted excess stress to it, and it's not functioning as it should.
 

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2005 gmc envoy_sle_xl
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Discussion Starter #4
I did not check out the transmission mounts. The best way I can describe it is it feels similar to shutting a diesel off.
 

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2007 chevy trailblazer_ls
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340 Posts
50 years ago I would know exactly what your problem is - carbon buildup in the top of the cylinders. Today's fuel injected computer controlled engines seldom have that problem. I'd sure try to old fix of highway speed for 30 minutes to blow it out. Can't hurt and won't cost much.
 

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I have the same problem with my '03 4.2L Trailblazer, 184K miles. New motor mounts this week helped the chassis noise & vibration, but the engine shut down continues to be very bumpy. It feels like a diesel that doesn't want to stop running for the last second after the key is shut off. The after-run clunking is reminiscent of bad motor mounts, but they're brand new. The mechanic that replaced my motor mounts said the trans mount looked good. Here's another possible clue to the issue: My vehicle has zero engine braking. My idle speed is 500 RPM and fairly smooth, but while driving, it must be around 1,500 RPM, as there is excessive pedal pressure required to come to all stops. I feel some reasonable engine braking at highway speeds, but virtually zero below about 40 MPH.
 

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Chevy Trailblazer 2008 LTZ (4.2L)
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178 Posts
I think these are just rubber engine mountings and they do not have hydraulic fluid inside as in the original mountings. This is bad :( These engine mountings serve a very short time and usually the vibration returns again.
 

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Thanks Vega_TB, my bad, I should have researched this before installing them. The motor feels smooth for now when it's running. Come to think of it, startup is not perfectly quiet or smooth either, so perhaps these new mounts are just not up to the job at all? I still suspect there may be some after-run type of issue at shut down, it shakes the vehicle.
 
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