I turn on my AC the car starts like shaking?

JASMINE000

MEMBER
2002 FORD FOCUS
4 CYL
AUTOMATIC
150 MILES

Hello as soon as I turn on my AC the car starts like shaking when I drive it the shaking doesn't feel anymore but as soon as I stop at a stop sign or light it starts shaking again. If I put it on "Park" it doesn't shake as much.

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

It sounds like you might have an issue with the idle air control valve (IAC).
The IAC is designed to keep the engine RPM at a certain level given the engine load. If the IAC becomes faulty it will impact the way the engine idles.
When you turn the A/C on it put extra load on the engine and a properly working IAC will trigger the engine to have a little higher RPM to cope with the extra load, if it does not increase the RPM the engine can run rough and in some instances stall.

Many times this can happened due to having a dirty IAC. Over time larger air particles stuck inside the valve and creates restriction inside the valve for the air to pass thru. This can impact the way the valve functions.
Severing the IAC by cleaning it out can solve some of these issue.

Here are couple of helpful articles:

https://www.2carpros.com/articles/how-a-idle-air-control-valve-works
https://www.2carpros.com/articles/idle-air-control-valve-service

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.

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