2015 Jeep Wrangler Unlimited Sport with 53k miles. No real issues to date.

Check engine light came on about a month ago. Pulled the code, P0302 so cylinder 2 misfire. Took to dealership to get checked, they said ignition coil caused the spark plug to go bad. Wanted $700 to replace the 1 spark plug so I left. Changed spark plug and ignition coil myself, check engine light came back on, same code. Swapped spark plug and coil between cylinder 2 and 4, check engine light came back on, same code (0302). Took to a Jeep guy local, they ran their test and no misfires were happening.

Any thoughts on where to go from here? My thinking is the issue could be the wiring to cylinder 2 or something else.

 

Note that the misfire monitor in the ECU uses the crankshaft position sensor to check that rpm does not sag any more than a specified amount when each cylinder is supposed to fire, so it can be triggered by any problem in that cylinder, not just an electrical misfire. If you have replaced both the spark plug and coil and are still seeing that code then you need to look at other possible causes for misfire, such as perhaps a clogged or intermittent fuel injector, intake or head gasket leak, etc.

 

I will put money on it that you have a worn rocker arm on #2 cylinder. you need to tear down and inspect rocker arms, even a little play on the roller will throw a p0302 code. if coil was bad you will see a small pin hole at the bottom of the boot where the arc occured. rarely it could need a cylinder head, do a leak down test and see if you have over 20% when rocker arms are off.

 

 

make sure they replace rocker arms also, if they don't you'll be back for misfire again.

 

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