Rough Idle

[jbeazell]

I know, pretty vague I'm looking to resolve a fairly noticeable rough idle. If I raise the idle speed up to about 900 RPM's, it smooths out to a purr. There is only an evap code, but that code is only recent, and this issue has been been getting progressively worse over the last 2 years. I changed out the dog-bone top/front motor mounts with some off an 06 Rendezvous, and that did nothing. Granted, brand new ones might be better, but I'd assume that this might give some level of improvement. It didn't.

Sound I look into replacing the engine and trans motor mounts, and even the top ones, with new ones? Is it possible that this is an indication of an engine issue, even though I'm not hearing anything else with the engine?

Personally, I don't care about it much, but I'm looking to sell, and I'd like to not have a washing machine for the buyer.

thanks!!

 

[melsg5]

You can try cleaning the throttle body and IAC.

 

[jbeazell]

I've recently replaced the IAC because it had an odd thing where it wouldn't hold idle on startup. The engine would fire up, and I could tell the IAC was lagging behind trying to hunt for startup idle, and then it would die. It would find and hold idle just fine if I held the throttle open just a bit on startup. That problem was eliminated after replacing the IAC.

I'll remove and clean out the throttle body and stuff this weekend. Any recommendations for a good cleaner?

thanks!

 

[melsg5]

No particular brand they all clean the carbon deposits. When you replaced the IAC did you notice any deposits inside?

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[chrisgblues]

Rough idle can also be caused by a defective fuel pressure regulator. It's a relatively cheap part, they break often, and they are not too hard to swap (at least on my 2005 Montana).
It's also pretty easy to check, just start the engine, take the vacuum hose off the top of the FPR and wait a minute or two to see if gas spews out the top (it's not supposed to). This may or may not be contributing to your problem but it's worth taking a few minutes to check.

 

[jbeazell]

cool, thanks