I have a 2005 PT Cruiser Convertible that's leaking oil in #4 cylinder causing engine light to come on. Now, I have changed valve cover gasket and tube seals, spark plugs and wires and coil, pcv checked okay, compression test on all cylinder was 120.

Still leaks in #4 and light comes on with code 304. Any suggestions?

  • What is the leak in #4 cylinder? If the compression test showed all the same what leak are you referring to? You mention a code 304, is that a P0304 or another type of code? How did you pull the code? Mar 27, 2016 at 18:27
  • The P0304 code and any oil leakage will most likely be two different issues. If you put a new sparkplug in and it didn't change how it's running, the issue isn't with any possible oil leak. How did you determine there is an oil leak? Mar 27, 2016 at 18:31
  • oil leaking in #4 cylinder,Sorry all the codes start with P0,so it is P0304,misfire in #4 cyl. Pulled plug ,dripping oil off plug.Turn the key three times then gives code,also Auto Zone
    – Doug
    Mar 29, 2016 at 3:31

1 Answer 1


From obd-codes.com:

A P0304 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #4.

A code P0304 may mean that one or more of the following has happened:

  • Faulty spark plug or wire
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Running out of fuel
  • Poor compression
  • Defective computer

I would recommend checking compression on your 4th cylinder. If it's really bad, it not impossible a bit of oil is seeping in there. It could be time for a piston ring replacement.

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