No. 2 Cylinder misfire

We have a 2005 OBW 2.5 auto that around 152 k miles, it threw a check engine light and the diagnosis was No. 2 cylinder misfire. We had the plug wires replaced with a genuine Subaru set since some arcing was indicated on one of the wires as well as new set of NGK platinum plugs installed. All was well for a while.

At around 154 k miles, it threw another CEL and the diagnosis was the same No. 2 cylinder misfire. Since we had new plugs and wires, the mechanic suspected either a valve improperly adjusted, carbon buildup on a valve, or a possibly sticking injector. He removed the valve cover and verified that the No. 2 cylinder's valves were adjusted properly and switched the No. 1 and 2 injectors to see if it threw a code on a different cylinder, thereby making the injector the suspect part. The diagnostics indicated the same No. 2 cyl. Misfire code even after switching the injector and running a can of Berryman B-12 Chemtool fuel injector cleaner through it.

The mechanic's diagnostic tool indicated a very irregular and intermittent No. 2 misfire after these things were done. He said that for it to throw a CEL, that it would have to misfire quite a few times and that just once or twice wasn't enough to throw a CEL. He cleared the CEL codes, gave me another can of B-12 and said to drive it until the CEL comes back on and bring it in for him to check it out.

We are both trying to replace the coil on this OBW only as a last resort since it is such an expensive part, but what else could the misfire be caused by? Any suggestions (or solutions) would be most welcome!

Well we've got the No. 2 cylinder misfire happening again. Our OBW has about 157K miles on it now. It threw a CEL, but hasn't been running rough or otherwise given any other symptoms. We took it to the mechanic who said that the diagnostic scan didn't have any other clues as to what caused the CEL on the No. 2 cylinder. Plugs, plug wires, the injector, and the coil pack all checked out fine. I personally checked the resistance on the coil pack and it is within specs. Since he had previously checked the valve adjustment, we knew that was OK.

Our mechanic suspects that it is a sticking valve on the No. 2 cylinder. Since the vehicle has so many miles on it, he recommended putting in a Jasper engine with a warranty. He said that he could do a valve job on this cylinder, but that given the OBW's miles, there would be no guarantee that the same thing wouldn't happen on another cylinder soon in the future. I have used this mechanic for several years and I believe that he is fair and honest. He hasn't called me back with an estimate on a Jasper engine yet, but I figure it will be over $4000, just guessing.

Any other thoughts as to what it could be without rebuilding or replacing the entire engine?

Thanks!

Given our situation, what would you do for this Outback that has a private party value of around $6500 or a trade-in value of around $4500? We need for this vehicle to last another 6 years to get our son through college reliably.

Thanks in advance!