Hi, I've recently purchased a 2002 volvo xc70. Didn't do it when I bought it, but soon after when I started it the next day started fine but the idle was a little around 1900-2000 rpm. Then it starts to go down to around 1600-1700 rpm then the engine quiets down and goes makes a thumping noise and shakes. Checked out the air filter was very dirty so replaced it and also used some engine restorer that seemed to work for a couple days then seemed to come back and was a lot quieter and the shaking was less intense. Now it comes back a lot harder and happens if the car has been sitting for at least like over 4 hours. Doesn't happen if I have been driving it and then start it up around under 4 hours it doesn't do it. I have talked to a friend about thinks it could be alternator, idle air control valve, or just cleaning out the whole air filter system. Anyone had this happen to them or just give me some advice on how to fix. Any things helps thanks in advance.

 

1. no

2. no, you don't have one, you have a drive by wire throttle, they don't need an idle control valve, that's what the throttle housing is and does.

3. no - sorry, find a friend that knows more about cars.

Try to describe you problem accurately and in detail - (normal idle speed is abut 750 rpms)

And don't buy any more engine restorer, snake oil , sea foam, or all purpose bull crap. Save your money for stuff that will actually fix something. With a 20 year old Volvo, you will need it.

Your shaking could be from a broken front or left engine mount - or an engine missfire - but without more details - we can't tell at this point. You might look to see if the mounts are having a problem. (of course you would need to know what a good ones look like)