Any ideas as to where and what needs to be addressed to cure fluctuating idle (900 or so down to 600 or so (V70 xc 2000 112k )

 

Likely your throttle position sensor is worn out. It is not replacable on your car you must buy a new throttle body (electronic throttle module) around $600 from what I've heard. You must have the dealer install it also as it needs to get programed for your vehicle. If it's a 2000 it's probably just comming off extended warranty. The problem will get worse if you don't fix it. It's very common problem with these cars. Do a search for volvo electronic throttle module. There is a software upgrade which increases your idle a little but only works once.

 

If the car drives fine, it is not the ETM. If the only time it fluctuates is at idle, you probably have a vacuum leak. Check ALL intake plumbing for secure fitment and for any cracks.

If the ETM fails, the car will still idle normally.

 

My idle fluctuated when my etm went bad. There was a bad spot worn into the throttle position sensor at the idle position. I can post a picture of the worn film if you like. That's why volvo's big fix was to change the idle a little so the tps would rub a little higher giving your etm just a little more life. But yes check the cheap stuff first, vacuum hoses first. The maf and the abs controller can also cause strange problems on these cars.