Intermittent p0303 cyl 3 misfire

Wethy

Wethy

Member
Good day folks.

Been dealing with an intermittent p0303 code. 2014 wrangler. Background. Been getting this code lately. ive been trying to sort it out. Ive checked plugs and coil packs as well. I did replace all plugs as it was nearing time to do that anyways.

But i was also getting a bank 1 post cat fuel rich code as well. Checked the injecters on bank 1 and they seemed okay. Replaced the cyl3 injector to be safe(may replace the other 2 as well)

It is driving fine but rough at idle. And since replacing the plugs it has gotten better. But still idles a bit rough.

Ill be doing a compression test in the next few days and maybe a leak down test also but im really curious if a bad/failing o2 sensor could cause a misfire(maybe due to the fuel too rich code)

Any other input would be appreciated as what to check. I cant check the timing chain without pulling the valve cover, and it may still come to that.

Ive also attached a image of the codes that come up. Screenshot_20200811-150729_Torque.jpeg
 
If it was dumping a lot of fuel I would check your cats for a restriction while your at it
 
Misfire will cause rich code. Concentrate on finding the misfire first. Switch wires and see if misfire follows. Switch plugs and see if it follows. Etc. etc. until you find it.


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A.J. said:
Misfire will cause rich code. Concentrate on finding the misfire first. Switch wires and see if misfire follows. Switch plugs and see if it follows. Etc. etc. until you find it.


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Click to expand...
Ive switched all coils around.And brand new plugs all around. Never switched cylinders on the misfire. Even checked for vaccuum leaks and the evap canister for potential issues.
cozdude said:
If it was dumping a lot of fuel I would check your cats for a restriction while your at it
Click to expand...
Ill have to pull the cat to do look but truely it doesnt seem to be running too rich. My fuel mileage, hasnt changed by more ten 10-15 kilometers per tank that i can tel( i did reset after i saw the rich code orginally)
 
Do the compression and leakdown test. Some of the earlier 3.6 heads had issues. Hope that isn't the case but worth checking. Pretty sure there is an extended warranty coverage on it.
 
Unfortunately the coverage doesnt extend to the 14s(even though mine has the same part number on the cylinder head) and it has 390,000KM on it. Ha ha so y'know it could just be done its life span af this point lol
 
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