Hi, I am in the process of replacing my coil pack on my 2003 automatic trans. I keep getting an intermittent P0306 (Cylinder 6 misfire and P0316 (engine misfire detected on startup first 1K RPM). I tested the coil pack and plug wire and they test OK. The plug wires are about 10K miles old, (I replaced the originals as a preventative measure) but it ran fine before and after replacement.

After I removed, tested and placed back the plug wire the issue disappeared for about 3K miles and now I am getting the same codes again. I do have a new Motorcraft coil pack, so I thought I would try that first if not I may have to remove the intake and send out the injectors for service as I have 260K miles on the truck.

On to my question, has anyone tried to place foil under the coil pack during installation as a shield to help with heat and to prevent degradation of the coil pack?

 

The coil generates its own heat so a heat sink grease would be better to use

Coil pack just has 3 coils inside, 2 spark plugs are fired at the same time, the pairs are 1/5, 2/6 and 3/4
Thats why the coil packed is wired the way it is
3 4
2 6
1 5

Those are the matched pairs
Try reversing 2 and 6 spark plug wires so
3 4
6 2
1 5
And see if problem moves to #2 misfire, P0302

If not then not a coil issue

I would do compression test BEFORE spending more money on spark or fuel
Because if it is a compression issue then you will be wasting time and money on non-fixes

Cold engine
Pull out all spark plugs first
Then test compression on each cylinder and write down results

 

Thanks RonD, Great advise as usual.

Will report back.

 

Update: Compression check tested within specs, removed upper intake manifold and removed injectors. I sent the injectors out for service and just received them back (see included shot of spec sheet of before and after service of the injectors)

I was not surprised to see that my #6 injector was not working but was surprised at how many of them had degraded in performance. I will be installing them in the next few days and report back.

Thanks RonD for your help.

 

Good stuff
Thank for the update and THE FIX

Never would have thought injectors
Still have my 1994 injectors, run a can of seafoam in the tank once a year and use cheapest regular gas I can find, lol
I guess "they don't build them like they used to"

 

Where did you send them for service?

 

I sent them "locally" to RC Fuel Injection www.rcfuelinjection.com 1711 Torrance Blvd. Torrance California 90501 (310) 320-2277 If anyone is in the area they are located down the street from Honda Motors of America

This is the second time I have used them with great service and excellent results. I used them last year when I had the intake manifold off of my 2002 BMW 330i and decided to send the injectors out since I had it apart. I also learned that they will test them at no cost.

No affiliation just a happy and please customer.

 

I have not tried seafoam but I do always use top tier regular gas (mostly Costco) and run a bottle of Techroline a couple of times a year with regular fuel filter replacement intervals. But I guess at that high of a mileage some things need attention at some time

 

Thank You!