Low Idle Revs? What can I do about it? Is it a problem?

Did the problem occur suddenly? Could be as simple as a vacuum hose that cracked or fell off. Dirty throttle body, misadjusted or bad throttle position sensor are also possibilities. I doubt it's anything major.

To be honest I am not sure when it started - I had some engine trouble with the cylinders about a month ago which turned out to be down to the coils - which were both changed.

Since then I have been noticing my revs moving about alot more than I did before - so it may have been happening for quite a while I just never paid attention to it before.

So I am much more worried when my car starts shuddering abit although it may have been doing it for ages I just never knew!

I have run alot of miles so would a dirty throttle body be likely? I am guessing its down to wear and tear that it gets dirty and the higher the milege the dirtier it could be? (although I am not even sure what a dirty throttle body is!)

what is the worse that would happen if it was left alone? and how long and how much would it cost to fix/check those possible causes you mentioned? Thanks.

Well the throttle body gets icky buildup from the crankcase ventilation system and over time that tends to clog up the small passage that lets air by during idle. It's also possible that the throttle position sensor is bad which could confuse it into thinking the engine is not at idle thereby disengaging the idle speed regulation. I'm not sure how much it would cost to have everything checked out but I always recommend having things looked at at the first sign of trouble, it may be no big deal but then again it may be something that will cost you a lot more down the road if ignored. Little problems pile up when ignored and before you know it a car is a beater.

I called Volvo and they told me it sounded like a dirty throttle body and that it would take 1 hour to clean and cost about £80! ($160!) which seems more than it should be!

I have noticed over the last two days that my revs have NOT dropped below

I do wonder though does a dirty throttle body account for the RPM moving about alot some days and not at all on other days? or would that be something else!?