Guys! This code is haunting me. I can't seem to get rid of it.

P0306- misfire on cylinder 6

So far I have replaced the plug and coil twice. Changed the injector. I replaced the Throttle position sensor, cleaned the mass air flow sensor, replaced the fuel filter, and replaced the VCT solenoids. I've checked the PCM connections about 3 times

At this point the truck is running good and I can only feel the misfire when I let off the gas and am going a few mph's. It gets some vibration but once I step on the gas it goes away or I come to a complete stop it goes away.

Now I do need to do the timing chain still. But I am trying to fix the p0306 before I start that project.

Also P0316 came up as well.

I am going to change the oil today and maybe run some seafoam through it. I don't know what else I can do at this point

 

I assume you replaced the boot and spring on #6... what plugs you using.. are you using dielectric grease? next would be a compression test...then check wires to cop and injectors

 

I did the compression test and it came back good. I am thinking I will switch the connection for cylinder 5 and 6 and see if it moves to cylinder 5.

As far as brand, I believe they are some cheap knock off brand from Amazon. They are one part. Coil pack and boot down to the plug. I got the whole pack for 65 bucks. But I've tried two different coils and the stock and it still comes up.

 

Or do you have a recommendation on how could I check the wires to the COP without moving it to another cylinder?

 

^^^^^^^ THIS ... and to add.

Something to keep in mind that might save you lots of trouble. If the problem is in the 'connector' or coil primary - your code will be P0356, not P0306. So since you have already tried changing coils - focus your attention on the secondary circuit beyone the coil... INCLUDING trying a different spark plug. We have seen plugs bad out of the box. And do a 'hospital operating room clean' job. NO greasy finger prints on ceramic or oily crap on Boots (should be new boots anyway). One could have been dropped / cracked internally in shipment or a number of things. And the 5.4L is VERY picky about plugs. I'm uncomfortable

 

You need to use Motorcraft plugs.

 

I used an autolite plug, then a motocraft, and then another autolite. I will throw in the motocraft plug tomorrow.

 

I've tried 2 different spark plugs since replacing the original. One autolite and one motocraft. Code keeps coming back either way. And I changed everything cleanly. What other secondary circuits would there be?

 

The only 'other' secondary circuits would be spring connections - which I trust would have been 'giggled' enough times to FIX by now with actions you have taken.

One other point of 'obscure' interest with P030x codes. The "ABSOLUTE" definition is NOT 'Misfire' as we mortals naturally interpret. The 'smart' PCM processer is so fast that it actually watches for the brief crankshaft rotational speed acceleration that "SHOULD" occur immediately after the spark event is commanded. If that crankshaft acceleration is not detected (IS BELOW SOME DIGITAL THRESHOLD), the PCM interprets that as a "Misfire". If you want to test this, you CAN actually install an old spare plug into the cylinder, plug the test spark plug into the coil boot, connect primary connector, connect a jumper wire from plug cathode to a good battery ground and crank the engine. PCM will be registering a misfire, but the plug should be sparking like crazy. I have DONE THIS to test a COP.

If a spark plug will not "ARC" - that would truely result in the PCM intrepreting it as a misfire per the above 'logic'. But consider all the other possibilities under which it might ALSO occur.

o- What if that injector was 'clogged' and not delivering enough fuel to facilitate ignition?
o- What if the Exhaust valve or one or both intake valves were NOT opening because of a roller/follower spit out of position prevent valve from opening?
o- What if compression was low. (I know you said compression was OK - but ?? what was it?)

If it were me, I would be testing the operational plug just plugged into the COP / boot and grounded to observe it sparking as mentioned above. If that test proves true - since you feel compression is OK, see what is going on with the #6 injector.

 

So I changed the plug and COP yesterday. Pretty much ran the same. However this time another code has came up.

P0340. Could this be the issue the whole time causing the misfire?

I ordered the parts for the timing job last night. Went with all melling parts besides the phasers. melling 340HV oil pump, MELLING3391SCC tensioners and chain. And fel pro gaskets sets.

I went with Standard motor products #S21001 for the phasers.

I am going to order a cam position sensor tonight and hopefully that'll fix the misfire?