What does the P0306 code mean?

This code is driving me crazy. I can’t get rid of it.

P0306 - misfire on cylinder 6

I’ve replaced the spark plug and coil twice, changed the injector, replaced the throttle position sensor, cleaned the mass airflow sensor, replaced the fuel filter, and replaced the VCT solenoids. I’ve checked the PCM connections about three times.

The truck runs well, and I only feel the misfire when I let off the gas and am going a few mph. It vibrates a bit, but once I step on the gas or come to a complete stop, it goes away.

I still need to do the timing chain, but I’m trying to fix the P0306 code first.

Also, the P0316 code came up too.

Today, I’m going to change the oil and maybe run some Seafoam through it. I don’t know what else to do at this point.

1 Like

Those misfire codes can be a real bear. Have you checked for vacuum leaks? They can cause misfires and sometimes only show up under specific conditions like coasting. Just a thought, it might be easier to fix than the timing chain! Also, that P0316 code could be related to the misfire, so hopefully fixing the P0306 clears it up too. Good luck with the Seafoam, I’ve had some luck with that in the past for cleaning things up.


The P0306 code in Ford vehicles means there’s a problem with cylinder 6 of the engine. It shows that the engine’s computer (PCM) noticed that cylinder #6 didn’t fire correctly.

I recommend performing a compression test on all cylinders to check for any significant differences. Low compression in cylinder 6 could indicate a mechanical issue such as a valve problem, piston ring wear, or a head gasket issue.

The P0306 code indicates that cylinder 6 is misfiring or randomly misfiring. Begin by checking for intake leaks; if no leaks are found, replace the spark plugs on cylinder 6.

Johnson, Ethan I appreciate you sharing your misfire code diagnosis knowledge. In fact, vacuum leaks can be cunning culprits, resulting in misfires that might only show up in particular driving scenarios. Examining vacuum leaks may provide a less complicated remedy than more complicated problems such as timing chain problems.

Hearing about your satisfying experience using Seafoam to clean engines is encouraging. With any lucky, fixing the misfire code P0306 also fixes the associated P0316 error, making debugging easier.

Have you ever experienced misfires of this nature before? If not, do you have any additional advice for identifying and fixing engine issues?