Vibration at idle ...when cold?

[ksmarshall]

2005 tb swb,4.2l,4wd.130,000 miles

After doing a lot of research , i believe that i may have bad motor mounts , when the truck is in gear at a stop i feel a vibration. i believe it to be around the 10hz that the roadie talks about (have never felt what a 10hz vibration feels like) but the vibration does feel high in frequency , when the truck is in park or neutral.. no vibrations.. seems pretty obvious that i should be looking into motor mounts.

the only reason i am second guessing myself is the fact it only does it when the truck is cold , once it reaches operating temps for 5-10 mins vibration goes away.

still pretty sure its the motor mounts just wanted to hear you opinions

its difficult for me to diagnosis issues on the TB cause its my wife’s truck and we work day/night hours during the week. will i notice the motor mounts to be bad with a pry bar or simply looking at them? brand for aftermarket or use an OE replacement , any suggestion /advise is always greatly appreciated

[navigator]

I would expect motor mounts to have the vibration when the motor is warm as well as cold, unless when they are warm they possibly expand enough to take up the slack. That much expansion seems like a long shot to me, especially with you living in FL.

If it is only when cold my guess would be that it is something fuel mix related.
Have you cleaned your throttle body recently with the battery disconnected so the PCM can re-learn the mix?
Have you recently changed the front 02 sensor? Sometimes they get lazy enough to affect the mix but not throw a code.
Is your gas mileage not what is expected?
Since it only does it when cold I would think your Tstat is ok but just to verify does your temp gauge read exactly 210 straight up when warm or a little to the left?
These are all common issues with our I6 that affect fuel mix and mpg which could contribute to the vibration.

I've got a vibration at idle, mine is the same in any gear at idle. It makes my radio antenna shake and you can feel it slightly in the seat of your pants.
I have cleaned my TB, changed my Tstat and 02 sensor which helped my gas mileage but haven't helped my vibration.
If I give it gas to like 700 rpm it goes away so I haven't worried about it. I figure if it is motor mounts it will get worse but mine has been pretty much the same for I would guess 2 years.

there are a lot of threads on the OS about this. You might want to look there as well.
here is one that sounds pretty close to what you have.
http://forums.trailvoy.com/showthread.p ... ation+idle

[The Roadie]

the only reason i am second guessing myself is the fact it only does it when the truck is cold , once it reaches operating temps for 5-10 mins vibration goes away.

You got it in one. As they deteriorate more, they'll do it even when warm. Use OEM only. Aftermarket ones have different dynamics and don't always solve the rotational harmonic issue.

[navigator]

if you read through that thread, you will find his issue was the motor mounts
I don't recall reading anything good about the aftermarket motor mounts.
Everything I have read says to go with the OEM motor mounts.
I seem to recall at least one member (on one of the 3 boards) saying they were out of stock but that might have been for the V8.

[ksmarshall]

I agree i believe it is the motor mounts , but just to eliminate a few questions , i have cleaned the throttle body unhooked the battery so the pcm may relearn, the thermostat was replaced about 6 months ago along with new fluids, the truck does only get about 14.5 for mileage(with stock tires/no lift) but its is mostly stop and go/city driving and a lead footed woman driving lol . i do think i may be looking into o2 sensors in my near future because of a seldom rough idle my wife is telling me about , i haven’t heard it yet but i am certain it is unrelated to my vibration issue.

may try an o2 sensor to help mileage and idle issue but will look at motor mounts this weekend

[The Roadie]

The motor mounts GM allowed to go out of stock were indeed the V8s.

[v7guy]

Are these trucks as picky about O2s as a lot of other GM products?

[The Roadie]

Yes. Aftermarket O2 sensors work fine, but the heater resistance is sometimes just outside where the PCM is programmed to throw a code. So to pass emissions and get rid of the code, just use AC Delco. But a bad sensor won't give you a 10 Hz vibration.