Vibrations when sitting in drive

[fadyasha]

Glad it you got it fixed! I have vibrations and all have been done except the mounts! Hopefully will get around to changing them.

Theyre weak but not toast as of yet

 

[Dakota76]

Hey all
My Envoy just started to vibrate at idle, worse when in reverse. Just wondering the location of the motor and tranny mounts.
Also is the any kind of a tutorial on changing them.
Does it being worse in reverse mean anything, is there a mount that causes this.

I can feel vibrations in drive but only ever so slightly.
Thanks Dak

Oh by the way
just changed my plugs The AC Delco ones
Change both diff fluids, transfercase fluids, engine oil and filter before the vibrating started.
Also did the throttle body cleaning but did not disconect the battery
After the vibrations started i flushed the tranny fluid

 

[Dakota76]

Well i disconected my battery and the vibrations seemed to have gone. Hopefully they stay gone.

 

[The_Roadie]

Well i disconected my battery and the vibrations seemed to have gone. ...

When I disconnected my battery, my engine stayed at a steady speed and didn't vibrate. Of course, the RPM was zero because it wouldn't start.

Seriously, sorry I was traveling and didn't reply. There is a thread around here with links to the manuals that discuss changing the motor mounts. But that's only in cases where you have a ten Hz vibration that's worse in DRIVE and not present in NEUTRAL. The RPMS will appear steady on the tach. Disconnecting the battery to reset the PCM after a throttle body cleaning is the tactic to take for erratic idle that fluctuates up and down from 600 RPM especially when the AC compressor cycles on and off.

 

[Dakota76]

Well after plugging my battery back in the vibrations never came back.(so far)

 

[paulcmartin]

Get out your electronic stoboscope? Borrow a high speed camera from Mythbusters?

Normal start-up idle RPM does indeed go down as coolant temperature comes up. This is the table built into the PCM:

Engineers are my favorite people. Thanks again for the diagnostic tip roadie