Rough idle when AC is on

[lahiruchandima]

Hi,

My Toyota Vitz 2007 idles roughly when AC is on. If AC is turned off, the idle becomes much smoother.

This vibration is more visible if I suddenly stop in traffic. As soon as I stop, several rough vibrations occur and then it becomes smoother.

I got the vehicle serviced: cleaned the fuel filter, replaced Air and AC filters, replaced engine oil. But the problem hasn't got resolved.

What could be the reason for ths?

[MikeCStig]

Basically your engine should be producing enough power to run the A/C compressor at idle... but it isn't. I'm guessing that this is going to be a matter of fuel or fire, maybe even both. If you haven't already checked the fuel pump, do that. Check the injectors and clean them.
Then the ignition system, make sure you're getting a good strong spark. If not, change the spark plugs, test the wires for continuity, and check the coils.
That's about all I can think of, good luck.

[Black Lotus]

Idle air control valve, clean or replace--maybe.

[lahiruchandima]

Originally Posted by Black Lotus

Idle air control valve, clean or replace--maybe.

As I know, vitz doesn't have an idle air control valve and it adjusts idle air flow by adjusting throttle position. So could this be a problem with the computer not correctly adjusting the throttle position at idle?

[shorod]

It could be a problem with a build up of carbon on the back of the throttle plate or in the throttle bore.

-Rod