Heavy Vibration in Gear

[dmunchak]

I have an '04 Envoy 4.2, I6, RWD.

New Plugs, New Motor Mounts, Replaced PCM, performed Case Relearn at local shop, throttle body is spotless.

I am still getting a very heavy vibration while in gear, also engine feels like it going to jump out of the hood when it is cut off.

ANy thoughts?

 

[nygiantsfan]

arcing through the coil pack boot, it's a long run to the plug. seen this with ford 5.4L doing this. may see a small tell tail puncture of carbon on the coil pack boot to the plug, i should show a misfire code,but it may not

 

[Heavyblaze]

Did you replace the motor mounts with factory one the aftermarket they say they vibrate more then the factory are best to get.

 

[MichEnvoyGuy]

Did you replace the motor mounts with factory one the aftermarket they say they vibrate more then the factory are best to get.

I made the mistake of buying Anchor brand motor mounts for my Envoy... it vibrated worse than the "bad" original ac-delcos. Returned them to rockauto, bought delcos, and the truck was smooth as butter after.

 

[dmunchak]

Motor mounts installed were factory.

Not throwing any misfire codes. I'll investigate the coil packs once the rain stops.

 

[The_Roadie]

I'd guess water in the spark plug well for #4 or small amounts of oil or water in any of them, except you already changed the plugs. Did you use Delco 41-103? Leaky injectors. carbon build-up? Have you ever tried injector cleaner or a Seafoam treatment?

Why did you change the PCM? A real problem traced to it, or just on speculation? Pretty expensive guess if that's the case.

 

[dmunchak]

Changed PCM due to the trouble code for "PCM failure". Repeated stalling at idle. Got a tuned one from pcms4less.