Vibration, occasional high idle, and other shenanigans in 2009 auto Yaris hatch

[tmontague]

If you have a ultra gauge or scan gauge and read your idle while the vibration happens you will likely see a fluctuation if 50 to 100 rpm.

It may not have happened before and it may have to do with the alternator but this is a common quirk of the Yaris. Chances are you will be chasing this for a long time and throwing way too much money at it for something that really isn't a problem.

Other option is to buy an OEM alternator, but like I said, it won't be cheap and it may or may not fix this quirk.

Many people have chased this red herring before and rarely ever seem to find a solution. Small low hp engines often need high idle rpm's to idle smooth while loaded, manufacturers dont want that due to fuel consumption so they tend to keep the idle rpm's as low as possible and this tends to lead to a vibration while the a/c compressor is running