Marvel mystery oil or seafoam

[famfeld]

I have a 2000 v70 n.a. and I have slightly low compression on 1 cylinder. I believe number 4 is at 130 psi and all the others are at 190. Besides that the engine runs well, and I have put 25k miles on the car. When I put a teaspoon of oil into the low cylinder, it quickly jumped to 210 psi. Every 1000 miles I have to add a quart of oil but very little noticeable smoke out the exhaust. Many people (non-volvo) have said to fill the cylinder with seafoam or MMO with the spark plug removed and let it sit overnigh with various different subsequent steps. They said it sounds like a stuck piston ring.
Any ideas?
Thanks in advance.
Feldman

[tryingbe]

They're cheap enough you can afford to try both.

Though, I'd run a leak down test to see where the air is leaking to first, the valves or the piston.

[splattj]

Seafoam will do a better job of breaking up carbon in my experience. I'd seafom all the cylinders, verify they all drained overnight, and then change the oil. Put just a little oil in each cylinder before you start it up since you'll have ZERO lubrication for the first couple revolutions otherwise.

[jurahd]

I’m trying to unstick a valve on ‘98 v70...just changed plugs no compression on two. Garage says it’s junk. So I rumble out on four cylinders and cruise high rpm low gear five or ten miles. She’s running , rough idle. Switched to premium chem in gas tank just driving around cel light on then blinking on load clear code when I get home po302. I can’t afford engine overhaul .Shame to lose it. But how much longer can I go? Is 10 or 20 k minus one cylinder possible ? 150k now.

[abscate]

Pull the fuel injector plug on cylinder 2. You don’t want gas washing down the cylinder walls.

Usually a single cylinder compression loss is a burned valve. A head job on a Volvo isn’t too expensive if you do the labor youself. I’ve got a fair amount of parts from the FDpP I can donate