I have an 01 Accord with a misfire problem. Started with cylinder 3 but now I'm getting misfire codes on both cylinders 3 and 4. I have 4 codes actually, Misfire in 3rd and 4th cylindersP0303 and P0304, Random cylider misifre P0300 AND Manufacturer Control Ignition System or Misfire P1399 The plug on the 3rd one is black and full of carbon but not wet. All the other plugs are clean and looking normal. I did a compression test today and cylinders 1,2,and 4 had 140PSI, cylinder 3 had only 70PSI. I squirted oil in the spark hole and compression went up to 100PsI in that cylinder. Can it be surmised that my problem is definitely worn rings or bad cylinder wall?


The motor is a 2.3L 4 Cyl Manual with 130K on it.

I guess Im still holding out hope that it may be a bad valve spring or something as I have yet to pull of the valve cover. Is there any possibility it could be anything other than the piston rings or wall with the compression test results Ive gotten?

 

It could be a problem with the valve/spring or the head gasket.

A leak-down will give you more definitive information on the reason for compression loss in cylinder #3.

 

Yeah I know I need to do a leakdown to confirm whats happening... Im guessing its not the head. I JUST bought this car 2 months ago and the dealer said they just had a new head put on it... although maybe it wasnt done well.. who knows. Im just hoping I can avoid an engine replcement as most shops are saying that is the best bet if there are piston issues.

 

Since it went from 70 to 100 that does indicate a problem with rings (or cylinder wall).

 

I wonder if the piston oil control rings are gummed up with carbon, is it likely a piston soak with GM Upper Engine Cleaner could help in that case?

 

With a new head they may have replaced it from the valves hitting the pistons which can damage the rings. I mainly have seen the oil control rings damaged but you never know.

 

I had a leakdown test done with inconclusive results... they did however stick a borescope into the cylinder and we could see that one of the valves was not seating properly. Without taking the engine apart I guess there's no way to know if it's the rings or the cylinder wall but either way looks like I'm better off replacing the engine than having someone tear it apart. I've been told cost-wise it would be about the same.