OK, did a compression check because of some symptoms (slightly rough idle, v. slow coolant use). Found #5 to be low. Buttoned it up and drove it, 1/2 later I'm getting a big miss and it's throwing codes for #5 misfire and cam position sensor issue.

I figure the #5 low compression is due to the rings getting carboned up from a failing coil. More on that later.

I'd pinched the cam position sensor wires under the cam cover (due to the harness sleeve being disintegrated). Soldered in patches for both wires and tie-wrapped them out of the way. That solves the cam position code issue.

During this time I determined #5 coil to be dead (verified via watching and swapping) and replaced it with a new one.

Drove it 40 min. tonight - running great. Accelerating from a light, it starts to misfire bad. Throws a #3 misfire...wth? Clear that code (yes I carry the frigging code scanner with me) and limp it home, missing badly.

At home, I see it's got a code for random cylinder misfire.

Also it gives me that burning plastic smell which I figure is from the now-fully-exposed wires over the cam cover.

Going out now to meter and test all the coils but was wondering...

- do coils fail all-of-a-sudden or gradually?
- did I reassemble something wrong, causing additional coils to fail?
- is there a driver circuit in the ECM that could be failing?
- any other thoughts?

Will post more after I diagnose more...tia,

Ron

PS '99 V70XC, 137K miles, Volvo brand plugs (prob new at 96K when I got the car)