I have a 2000 S70 GLT that has an idle problem. When in park the idle fluctuates from around 500 RPM to 1000 constantly. It oscillates between 500 and 1000 PRM around every 2 seconds or so in an almost rhythmic manner. When driving the idle is around 800 and fairly constant although sometimes will oscillate between 750 and 850. Also sometimes when I come to a stop the idle will get real low and feel like it might stall although it hasn't yet. I cleaned the throttle body and have done general maintenance. Any thoughts or solutions? Thanks

Just replied to a very similar question on another thread with this -

I am having the same problem, had the car plugged into a code reader and it showed a MAF fault, so I am about to remove and clean it.
However I have been told that the real fault could still be the ETM - even though there is no fault code or ETM light on the dash.
The MAF is probably a good place to start, if cleaning doesn't work a new one is around $250.

Hi
Check for cracked vacuum pipes or missing blanking caps on any of the pipes and tubes around the inlet manifold which could allow air into the inlet system. This is often the cause of a fluctuating idle. Alternatively the idle stabilization valve could be sticking and need cleaning. This was a common fault on some Audi models but I've never yet come across it on a Volvo.
Cheers.

ETM is an ongoing problem

http://www.channel4.com/4car/ft/feature/top+ten/179/5