I have a 2001 V40 with ~157000 miles on it. Yesterday I hit the gas hard to pass someone on the highway, the car started surging and the CEL started flashing at me. Scanned the car, came up with P0303 cylinder 3 misfire and no other code. I changed the plugs, no difference, changed the coil that runs cylinders 2 and 3, no difference, then I swapped injectors between cylinders 2 and 3, problem stayed on cylinder 3. Now I'm baffled as to what it could be. The misfire according to the computer is only on cylinder 3 but changing all ignition and fuel to that cylinder has not changed the problem. Can anyone help me with this issue?

 

Sorry, I forgot to add, the misfire is only under heavier acceleration and occasionally at idle with the transmission in drive sitting at a light or in traffic. Low load idle and normal acceleration seems to be normal.

 

Are your coils cracked? Volvo plugs?

Like you said, if you have good fuel / air, and spark, then that leaves compression.

 

Coil for cylinder 2/3 is new so it better not be cracked, and it's only misfiring on 3, so it somewhat eliminates the coil as the problem since it would be missing on 2 and 3 if the coil was screwed up. The plugs are Bosch Platinum Pluses. I was told that platinum are OEM for that engine. The only other thing I can think of is carbon buildup on a valve. It's my mom's car and she drives it easy all the time and generally short distances of less than 5 miles. It's not smoking at all so I doubt it's a ring or guide, but who knows, I'm a VW guy myself and they have a completely diffent set of problems. Are there any sensors that could be causing a problem only on cylinder 3?

 

I realize that this is an old post, but I just experienced the same thing. 2001 V40 with 139,000 miles.
I was actually posting PO301 and PO304 and also replaced the spark plugs and then the coil. Still running really rough. I brought it to an honest mechanic today who asked me if I cleared the codes. I replied that no, I don't think I did but I can feel that it is still bogging really hard. He told me to clear my codes and go for a drive. I was sure that I could get it to code up again, but so far nothing. Fingers crossed.....60 miles and counting. Lesson learned: Clear your codes.