Hi,

I have a 2003 F150 4wd 4.6L V8 with 92K miles. A week ago, it was getting a very strange feeling while driving. So, after a couple days, the check engine light came on. I read the DTC code as "misfile on cylinder 6", which I believe was code P0306. Well, I had no choice, I drove on it for a couple days.

Today, I replaced all 8 spark plugs (phew, those ones in the back are hard to get!). I was deathly afraid of cross-threading them, but don't think I did. Anyhow, I cleared the DTC code and drove it about 2 miles. So far the computer hasn't responded with any errors, so that's good.

When I replaced cylinder 6 spark plug, the hole the plug was in seemed to have liquid in it. I don't know if it was fuel or water, but it definitely wasn't right and wasn't in any of the other ones. So, that explains the misfire I guess.

Now, when I took it on the test drive, the idle is a little rough. It isn't a constant roughness, more like an uneven roughness. After a couple seconds, I'll feel like 3 or 4 bumps, then nothing for 10 seconds, then a couple more bumps, somewhat of a cycle like that. This wasn't happening a week ago before I started having a problem.

Do you have any ideas? If I cross-threaded a sparkplug, would I know it right away? Would it throw a DTC Code?

Also, where in the heck is the darn PCV Valve? I want to replace it too.

Thanks,
Tom

 

did you replace wires also ? could have broke a a plug wire or contact ?

 

When/where do you find plug wires on a 4.6 or a 5.4 COP motor later than 2002?
Rough idle involves the mass air meter, vacuum leaks, more fluid in a plug well, water in the gas , IAC., coil plugs, injector plugs etc.

 

i have had a couple small antifreeze leaks taht got fluid into #1 and #3 plug holes a year apart. both times the code finally came up. it will if it gets bad enough. the fluid forms a path to ground for the coil and it will not fire the plug when grounded. i cleaned the coil and that helped, but eventually i had to replace both COPS. I think if you replaced the COP you might fix it. If it gets worse and you get a code, see if it is that same cylinder. Did you put the same COPS in the original position?

 

Thanks for the response.

I did not replace any of the COPS. I did the spark plugs one at a time, so they should all be in the same place.

I noticed while driving that I am getting a lot of exhaust... If the liquid fell through the spark plug hole that was in Cyclinder 6's, that might be causing this roughness? I would think it would work/burn it's way out.

I put in some fuel injector cleaner, maybe that will help.

2 other questions.
1. Is it possible i cross-threaded a spark plug?
2. Any idea where the PCV valve is?

Thanks,
Tom

 

You motor does not utilize plug wires because it has the COP(Coil On Plug) ignition system.



Our new Ford COP’s, the Sultans of Spark(S.O.S.), have
been designed with both durability and performance in mind.
Please see them at:
http://www.performancedistributors.com/soscoils.htm
Quality was the main feature we stressed when we went to the
drawing board on these coils.
See your FTE special at:
https://www.ford-trucks.com/forums/793806-cop-fte-special.html#post6780133

 

The PCV valve is on the passenger side valve cover as for the other question i do not have an answer for you sorry.

 

If you have water in the plug hole, I'd guess that the COP is shot. You could try changing it out. I changed all mine at 90ish with Ebay coils. They were $99 for all 8 and have been working fine in all kinds of environments for the last 10K or so.



Mike

 

If you cross threaded a plug, you should have felt it not going in easy as it should have.
If the plug threads are leaking or the plug body has not sealed it's taper seat, it will blow pressure into the well and burn the boot then the resultant end result.
If there is a leak on to of the engine from coolant it may well find it's way into a plug well.
Coolant out of a cylinder to long a time can damage Ox sensor as well but a code should be set if this has happened.
You need to go over things a bit more to see if you have another issue.
Our crystal ***** are not that good!

 

I'm going to switch COP 6 with COP 2 and see if 2 starts misfiring.

 

switching COPS is a good test, but you need to have a code first or how will you know it moved to another cylinder? #3 is 303, #6 is 306 code.

 

You are correct. I did get a P0306 code that got thrown on my way home from work.

I ended up switching COP #2 and COP #6 and cleared the code. After a 15 minute test drive, no code yet, but the idle is still there. It will come forth on my way to work tomorrow. I hope i get a P0302!

Thanks for your help,
Tom

 

So, I got the check engine light after switching COP 2 with COP 6. I want to change out some fuel injectors now. Any tips?

It looks like the fuel rail is held on with 2 bolts and should pop off, then I just need to pull out the injectors, grease the orings, and put back...

I'm hoping it's that easy...

Tom

 

What code did you get? I'm not sure why you're switching injectors around. It sounds like you're jumping all over the place.

Mike

 

I keep getting P0306. First I changed the plugs. Second I swapped COP's 2 & 6. Third I swapped injectors 6 & 7. If the problem was the COP, I would have gotten a misfire on 2. If the problem was the injector, I would have gotten a misfire on 7. They are quite logical things to try.