04 Rough Idle in Drive

[droos]

I bought a used 04 TB, 4.2L, 2wd, w/ 46k miles on it. It runs fine but in drive with the brakes on it vibrates and I hear a low frequency rumble. The vibration and noise goes away as soon as the truck moves. Any ideas?

[maxwedge]

Tough to help with this sitting at our desks, possible exhaust grounding, engine miss at idle some rotating component on the engine noisey, someone has to check this onsite.

[droos]

Based on the lack of replies it appears this is not a chronic problem.

More info: The idle rumble does not happen in Park only in Drive with the brakes on. It seems to get louder a few seconds after stopping.

[droos]

The problem was the engine mounts. Replaced them and it purrs. Rough idle is gone.

[maxwedge]

Thanks for posting back, but what was wrong with them?

[droos]

I don't know the specifics. The dealer (not GM) I bought it from could not determine the problem. They sent it to the local Chevy dealer. They diagnosed it as broken engine mounts. I was a little skeptical but they were right. They replaced both of them today and the rumble & vibration is gone.

[maxwedge]

I 've never seen or heard of this, if it were me I would be suspicious of this truck's backround, not to be an alarmist though.

[droos]

Now you have me worried. I do know this TB was in a fender bender that got the front right. It was fixed professionally. My mechanic inspected the car before I bought it. All he found was that it needed a front-end alignment. It was a local one-owner.

If the broken mount is a sign of bigger problems, what should I look for?

[maxwedge]

How did it break, this is not a normal interval or maintenance item, something occurred to cause this, they are just not made in such a way that this fails., maybe in 15 years. I'd ask for the old one or get someone, maybe in a body shop, to closely at the frame and under chasssis.