Air con causing rough running problem

[V0lv0Craig]

Hello

I bought a 2000 plate S40 1.8 petrol manual model today. On driving it home all was fine until I put the air con on and all of a sudden the car started running rough making a jerking motion and seeming to almost cut out. When I turned the air con off the engine was running sweet as a nut again.

It's covered 100,500 miles and has part history. The cam belt was replaced at about 54,000 miles. I am going to have an oil and air filter service and hope this resolves the issue.

I really love the car and the engine doesn't miss a beat apart from this.

Any ideas gratefully received.

Craig

[oragex]

Sounds like the a/c compressor has seized. Perhaps there is a leak somewhere and the oil and refrigerant have leaked out.

[alschnertz]

An oil change will not make any difference with the "jerking motion", but it's a wise idea with a new (to you) purchase.
Unless the air filter is awfully clogged, that will not likely make any difference either for the "jerking motion".

However, before you start throwing money at this thing, here's a few questions...
What were the conditions when it started the "jerking motion"?
Were you at idle or driving on the interstate?

With that mileage, I would clean the IAC (idle air control) valve before anything else.
It would probably be wise to clean the MAF sensor (spray cleaners only) and the TB (throttle body) as well.