Cylinder 4 misfire Code P0304

[agu7]

I have a 2015 Journey Crossroad 3.6L with 94,000 miles, an a code P0304 cylinder 4 misfire.  After doing all things mention below, the engine runs smother and it fills with more power....however, when I start the engine or while I'm at a stop light the RPM's are between 500-600 too low. And the Scanner still reading the same code.

 

What I have done to correct the issue with no luck? 

- I swap coils 4 and 2

- replaced all 6 coil-on-plug insulator boots with new ones

- replace spark plug #4 with new one

- cleaned all fuel injectors (I removed the injectors and cleaned them with a wire brush, and also connected a cleaning line tool with the straw to the fuel line and a carb cleaner)

- cleaned O2 sensors

Note:

At 90,000 miles (3 months ago) I replaced the oil/cooling filter housing with gaskets, replaced oil & filter, replaced all spark plugs and the pcv valve.

I can't find any air leaks...

 

Any recommendations? Thanks in advance  

 

[5rebel9]

Pulling the fuel injectors and "cleaning" the nozzle tips (particularly with a wire brush) is not the best way to handle that situation. The spray pattern is done internally in each injector. IF there was that much "gunk" on the injector tips to warrant you trying that, then I'd surmise that there is an excessive amount of intake valve deposits and internally "gummed up" injectors to warrant using a can of Seafoam in the fuel tank and a good LONG drive at highway speeds. Note this is NOT an "instant fix" cure, but more cost effective than new injectors and cylinder head removal for decarbonizing.

[agu7]

I been using seafoam for long time, and now, after the 75, 000 I use the high mileage seafoam every 10,000 miles in all 4 cars. I will get another can, and will keep you guys posted.

 

Thanks again. 

[John/Horace]

Compression on cylinder 4 would be useful information.

 

When you did oil cooler housing (like a lot of us also had to do) you had upper and lower manifolds removed.

 

it’s a good idea to replace both sets of gaskets at same time, the old  gaskets get crushed a bit. Air leak from bad intake manifold seal can create a cylinder misfire code sometimes.

 

 

 

[agu7]

John, I did replace both sets of gaskets at the same time. 

I swap the injectors as well, erase the code and keep giving me the same reading "cylinder 4 misfire".

I'm going to check the compression now.

[tsteves5]

I had a similar issue on a Town and Country with the same 3.6 engine.  In my case it was a consistent cylinder #5 misfire DTC.  It would run rough at idle, but smoother at speed.    I ruled out the spark plug, coil, injector, computer, and upper cylinder head components.  The results of a compression test were acceptable.  In the end, it was ultimately a bad piston ring.  While it would make acceptable compression on that cylinder, it would not hold compression very long.  So using a simple compression tester did not show anything wrong.  It ended up being a leakdown test on that cylinder that revealed the problem.  I never skipped an oil change or any other maintenance so I'm not sure how the ring became damaged.

 

I hope this isn't the case for you, as that's a MAJOR repair or possibly even an engine replacement.