Cylinder 6 misfire on 2010 Volvo S80, p0306 code

[cassielane1990]

Hey all,

I have a 2010 Volvo S80 (3.2) with just under 208,000 miles on it.

Recently I have been experiencing an issue - only on a cold start in the morning - where the car has a rough idle/vibration which smooths out after about 30 seconds. After this point, the car runs/starts fine. I went and had the codes scanned: two popped up for the cat converter, and one for a misfire on cylinder 6: p0306.

I took the car to Mechanic #1. He replaced the ignition coil on cylinder 6. Cleared the codes.

A week later, the code/symptoms reappeared. I took the car to a Mechanic #2. Again, his solution was to replace the ignition coil on cylinder #6 and the spark plug. Took the car to AutoZone to have the codes scanned and the only codes that appeared were for the cat converter. No misfire.

That brings me to yesterday. I went and had the codes scanned yet again and voila, it's back: p0306.

So, Mechanic #3 today pulls out the coil, pulls out the spark plug, sees a little bit of oil on the spark plug, and says that means either a valve seal is leaking oil on the piston or there's a problem with a piston ring. Either way, he said this fix would be expensive and, I quote, "Don't put any more money into it. Start saving for a new car. Ride it until it dies."

I have dumped tons of money into this lovely machine over the nearly ten years I've owned it. Among other things, the ignition coils, alternator, radiator, and virtually the entire cooling system has been replaced. But I'm totally stumped by this p0306 ordeal. I have no idea what it is at this point, what to do, or if Mechanic #3 is right and I should just start looking to trade it in. I'm out of ideas and running out of money.

Any advice is appreciated. Thanks!

[pgill]

The PCV on the 3.2 routes to cylinder 6 then 5, 4, 3, 2, 1

I would confirm that the PCV is working (and replace it as needed if it is not)

I also checked the misfire count and it was 1 misfire on one of the cylinders and all of the others were ZERO.
This is normal my LR2 will have a random misfire typically on a cold start.

I am sharing this because its been about 7 months and over 5,000 mile and everything is stable.

The only significant change was the PCV replacement.
An aftermarket part but marked with FOMOCO.

The replacement PCV seems to have made enough of a difference that the Sparkplugs are no longer getting oil fouled and setting misfire codes.

I do have two Sparkplugs with a hotter heat range on the shelf just in case but so far they are not needed.

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Good luck

Paul