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09 chevy Silverado irregular idle / rough shift

I just bought a 2009 Chevy Silverado , have only had for a week and have noticed an irregular fluctuation in idle, also the transmission has lack of a better term jarred a few times and seems to downshift rough sometimes. The irregular idle seems to be worse when the ac is on, I can hear the compressor kick on and off alot. And just once I was driving and tried to accelerate and it didn’t want to very much. Factory warranty is out and dealer didn’t give option for extended warranty. They have agreed to look at it but aren’t willing to do much other than clean injectors and throttle body. Any advice or ideas on what the issues might be ?

How many miles?


Mild idle issues and little weird shifting would rarely amount to any major warranty issue. Most often these things come from basic maintenance types of things or other minor wear and tear kinds of things.

First make sure all of the basic maintenance stuff is up to date. It’s in the owner’s manual, and 60K often includes lots of things. It might, for instance, include things like new spark plugs, and a new fuel filter.

If the AC kicks on and off a lot that usually means the pressure in the system is low. So you might have a minor leak of some kind. But a shop can check the pressure and, if needed, add some extra refrigerant with dye in it.

I think this has an electronically controlled throttle, in which case, cleaning the throttle body for a wonky idle is a good first step along with checking for any vacuum leaks. If it’s not an electronic throttle, then add the idle air control valve to the cleaning.

A wonky idle can easily make the transmission downshift a little funky sometimes. But if you really want this transmission to last the best idea is to drop the pan and change the filter every 30K miles or so. In which case, you’d be due for the second service for this truck. My guess, however, is that its never been serviced. Now would be a good time.

Very helpful thank you, unfortunately the truck doesn’t have the owners manual, one other thing is when the let off the accelerator and then get back in it it hesitates before accelerating

The hesitation can also be the throttle body (or other simple things like old spark plugs)

You can often score full pdf owner’s manuals (or at least service schedules) online someplace. I’d just start with GM’s website. If they don’t have it, general internet searches would probably turn one up.

Ok great info, thank you

I am leaning towards a cleaning of the maf sensor, new air filter, I think plugs are good to 100k, I am not sure about gas filter, weather it is lifetime in tank, or replaceable. A treatment with techron or sea fome and a nice long highway drive will never hurt anything, and may help.

Ok thank you