oil-change cause rough idle?

Unscrew (torx bolts) the plastic cover for the spark plugs, and check for oil spilled when the engine was re-filled. Spilled oil can seep under the plastic cover and collect around the spark plug leads/coil packs/plugs. Also check for loose/unseated cables which may have been moved when cleaning up such a spill. (Don't mix up any cables if removing them to clean/re-seat). I've had uneven running occur just as you describe, a couple of times in the last 2 years on my 960, shortly after an oil change or inadvertent spill during topup. After careful cleaning with a paper tissue and re-seating any loose electrical connectors, the car returns to normal, very smooth, running (now at 125k miles).

Your source on vacuum tubes is also correct though, they're just harder to check - there's a junction box of vacuum tube pipes somewhere (lower-right engine compartment? it's too dark to check here just now), one tube could be broken/perished after movement during general wiping up of oil spills etc. I'm told faulty vacuum pipes are harder to detect and replace.

Good luck. 960s are still great cars when they work, just a few more th> per our '97 volvo 960 wagon, we had the oil changed at a drop-in

They may have knocked loose a vacuum line, it's not a Volvo specific problem but if there's lines in the vicinity of the oil filter that's where I'd start, just a good look under the hood with a flashlight should determine the state of those.

ascott: many thanks your good suggestion. a non-volvo mechanic (nephew of a close friend) said he'd give it a quick look-see tomorrow and i'll give him your note. if he can't find the problem, we'll have to move it along to a guy named olaf with an obdii scope. fyi, i took it out on the freeway today and then around the town and you'd never know there's a problem except at idle. smooth as an icy blast of absolut. am

The problem only at idle really increases the "vacuum hose" suspicion.

Mike

the mechanic is reporting an unhappy coil. not sure how that could affect only one cylinder instead of all six. we'll see. thanks all for your observations. art

I don't know when they started doing it but my S80 has an individual coil for each cylinder (connects directly to the sparkplug, no high tension wire)

Allen

folks: again, many thanks for your input on this query. it turned out to be a bad coil. all best, art

p.s. i am unable to determine the root of the coil problem, whether nature or nurture.