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I've had this 09 impala for a little over a year and the whole time I've had it I've had this problem. When my car is idling it has a small rpm jump and shakes. It's not a constant shake. But it will shake a second then stop. Then shake. Then stop. It never goes away in idle. The car runs strong. I've never had any issues with the perfromance. I took it back to the dealer a couple weeks after buying it and they claimed they didn't see a problem. But my car should not be running like this. Its not causing issues but it's rather annoying and makes me feel as if the engine is not healthy. Any input would be appreiciated! Thank you.
 

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What engine do you have, and how many miles?

I have an 08, 3.9 with AFM and I got the occasional RPM jump (about 50rpm) and slight shake at idle. It's not always there, but it does happen once in a while. I've had it since I've had the car. I tried to find the source of the occasional shake and RPM jump, but I wasn't able to. I checked injectors, throttle body, MAF sensor, MAP sensor...

Since it was never serious and since if I blipped the throttle to about 1,500 RPM it would stop happening, I never thought about it. Dumped another bottle of fuel cleaner in there and I kind of forgot about it. Although, if I think about it, it seems the rough idle / shaking hasn't happened in a while. Maybe I've just tuned out the shaking lol.

I'll see if it's still around on my way home from work today and get back to you. Maybe the repeated injector cleaner treatment worked. *shrugs*

Have you tried an injector cleaner? A can of Seafoam, or Jectron, or Techron. Some people call it snake oil, some people swear by it. It may be helpful if your symptoms are similar to mine, which they seem to be, except for the "never goes away" part.
 

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In addition to adding fuel injector cleaner (Techron is excellent) - you should clean the inside of your throttle body. If the edge of the butterfly valve and/or the wall of the throttle body is dirty, it prevents the adequate flow of air past the butterfly valve at idle. This causes a rough idle (not enough air) and "hunting" by the computer to stabilize the idle.

You can buy a can of spray throttle body cleaner (do not use carburetor cleaner which can damage oxygen sensors) and spray the inside of the throttle body with a cool engine (off) until it runs clear out of the throttle body. You can put rags and/or paper towels under the throttle body (after disconnecting the air inlet duct). The throttle body is a "drive-by-wire" type which can be damaged if you manually move the butterfly while the engine is turned off.
 

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Also - make sure your air filter isn't super dirty if you haven't replaced it recently...

Sent from my Hi10 pro using Tapatalk
 

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While we're at it... When was the last time a tune-up was done? Plugs, plug wires, air filter, etc? All these could cause rough running.

Edit:

I forgot to mention earlier that I personally love the fuel treatment stuff. I dump a bottle in every six months. I found Techron, like what @1999 White C5 Coupe said, has worked best for me but I have a bottle of Jectron on the way to see how that compares. It's got great reviews and is apparently a stronger cleaner than Techron. We'll see!
 

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Also make sure you post this in the gen 8 section where you might get even more help.
 

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I've had this 09 impala for a little over a year and the whole time I've had it I've had this problem. When my car is idling it has a small rpm jump and shakes. It's not a constant shake. But it will shake a second then stop. Then shake. Then stop. It never goes away in idle. The car runs strong. I've never had any issues with the perfromance. I took it back to the dealer a couple weeks after buying it and they claimed they didn't see a problem. But my car should not be running like this. Its not causing issues but it's rather annoying and makes me feel as if the engine is not healthy. Any input would be appreiciated! Thank you.


What did you determine and/or resolve?
 
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