junk405

2013 C250 coupe sport 1.8 throws p0301 #1 misfire new plugs switched ignition coil pack with #2 still show p301

antboii

hey man,

if you haven’t changed all the spark plugs and coils I suggest you do that. They all work in tandem with eachother and if one is out that means the others have to work harder to pick up the slack of the misfiring cylinder.

that would be my first suggestion is to do an ignition service.

ant

junk405

changed all plugs switched coil #1 with #2 and still showed #1 misfire

antboii

​​​​@junk405

​​​​​Did you clear the code after you changed all the plugs?

It could be your coils that are bad as I also suggested previously.

Did you visually confirm there is no spark going to that misfiring cylinder plug?

Ant

junk405

changed all plugs cleared codes still came up #1 after switched coil with #2

junk405

checked #1 has spark

antboii

​​​​​​I Would look at injectors next then. Since you're confirming there is spark and the coils are good.

IS there any oil collecting/pooling in the spark plug hole? You could have oil collecting and causing a miss fire. Was the plug/coil oily when you pulled it out? This would be a failed spark plug gasket on the valve cover. There is 4 smaller gaskets that surround each coil and plug.

Have you ever done a fuel treatment? Or replaced the pumps in the tank? That's where the fuel filter is located. Best case is a dirty injector.

Ant

junk405

20 lbs compression on #1 120 lbs on rest of cylinders?

chassis

Change all coils.

Check cam sensor and cam magnet electrical harness connectors for signs of oil.

Check O2 sensor connectors and injector connectors for signs of oil.

Does this engine have tumble flaps in the intake manifold?

antboii

I was going to suggest next a leak down test and or a compression test. It's never a good sign when you have to start pulling out those tools

Did you perform the compression test?