I have a problem I have been chasing for a while. My 2000 Dodge Caravan 3.0 has a problem with P0305 misfire cyl 5. I have changed plugs, wires, coil, cap, changed and cleaned injecters, changed injector O-rings, swapped around the injectors, run tons of Seafoam through the vaccum and in the gas, and it is always cylinder 5. Any suggestions as to what to look at next? Thanks

 

Carbon fouled intake valve. Fairly common problem with this engine. Makes sense that would cause the same misfire code after replacing all those parts.

 

Thanks for the response! what would be your recommendation as to the best way to fix this?

 

did u do a compression test? cuz if you have a bad valve all that stuff you thru at it was a waste of $ i know cuz i fixed a 3.0 van in tech school that came to our class with all new parts and i figured out that all the pro mechanics that threw parts at it never did basic testing and compression on the bad cylinder was 70 while the rest were 150. pulled the head and found exhaust valve was burned slightly

 

Shelby is absolutely right.

To get a clear diagnosis, you'll need to do a compression test. A dry compression test tests the valves, a wet test tells you the condition of the rings. But in the case of a carboned, burned, or bent valve, you may have to do a "snap" compression test. That's done on a running engine.

Start by doing a dry cranking compression test and record the readings for each cylinder. Then remove the valve core from your compression gauge, ground the spark plug wire and install the gauge in the suspect cylinder. Start the engine and record the highest reading while at idle. It's usually about 50% of the cranking pressure--that's normal. Then snap the throttle open quickly to wide open throttle (this is really a quick snap procedure--don't let the engine rev up too much). Record the highest compression reading. It should be about 80% of the dry cranking reading. If it's a lot less, especially if it's just one or two cylinders that read low, it's an indication of a valve problem.

If it's just carbon, you can try adding Seafoam to the gas. Probably won't work, but also not a big $$$ risk. Otherwise, you're looking at a valve job.

 

Thanks alot for the advice and best recommended procedures to diagnose this problem. Guess I just need to bite the bullet and look at doing a valve job. I will do the compression test with the procedure you recommeded RickMN and let you know the results (prob. be this coming weekend). Thanks again for the help.