I've had my S40 for a few weeks now and have noticed a vibration when the car is idling. It's worst when left in drive, but also shakes a bit while in neutral.

The steering wheel and dash board shake noticely while the car is idling, however everything is fine when driving. Any ideas what it could be?

Check you engine mounts.The R/S engine mount is known to go bad pretty often.Also check the engine mounts located under the engine that go to the crossmember.Sometimes the trans mount goes bad to.

I had Volvo check the engine mounts and they advised that they were fine. The only problem they could locate was a faulty oxygen sensor, but I don't think that would have anything to do with it.

I spoke with a mechanic friend of mine and he told me to have someone check the flame trap and that it sounds like a vacc leak. The I remembered that the person I bought the car off mentioned something about an air hose needing replacing, although Volvo didn't tell me this after they serviced it. Could a busted hose cause this problem?

Thanks

Yes a broke hose could cause that problem.Make sure you check all the hoses good.You can use carb cleaner and spray around all of the hoses if the idle changes you found the leak.

Thanks, i'll take her up to the mechanics tomorrow. I can't believe Volvo didn't find anything, they even told me that it was normal for the 2L to shake like that!

Let me know how you make out.

Well still fighting this problem.... Apparantly it's a common S40 2.0 problem due to an engine inbalance that Volvo have no idea how to fix. Replacing the front engine mount will mask the problem, but I'm not sure how much of an ordeal that is. For a non-volvo mechanic to replace it, would this be considered a big job?

It is no that hard to do.It could probably be done in about 20 min from start to finish.
If you have a floor jack you can do it your self.