P0306 CODE - V6

Looking for some guidance...

We have a 2004 4th gen, V6 with 159k miles. Just threw a P0306 misfire code on cylinder 6 the other day. The car will run a little rough for about 4-5 seconds on a cold start then smooth out and is fine. I topped off the radiator about 500-600 miles ago and it has not dropped at all. No smoke out tail pipe, engine oil looks fine, engine oil fill cap also looks clean. Car has also never overheated. After the P0306 code I did swap the coil packs from #6 to #4 to see if the code would return on the same cylinder. So far code has not re-appeared but I am assuming it will soon. When I pulled the #6 cylinder coil pack I did notice a thin layer of oil which is telling me the valve cover seals are bad. I don't think the oil is causing this P0306 code to happen because once it clears out the car will run fine for the duration of driving. Then once it cools down cycle will happen again.

My question is what is the best way to diagnose the problem? I know it could be a head gasket, intake manifold leak, bad coil pack, injector, bad plug wire. I am aware the V6's have head gasket problems, but I would think coolant loss after 500 miles would be a symptom of a head gasket problem.

Any help would be appreciated. To make things a little more challenging this is my sons vehicle and he is away to college, so he has very limited tools to diagnose. I am open to taking to a shop to diagnose but finding a trustworthy skilled mechanic is tough these days.

Thank you...

 

My gut says a sloppy injector when cold. You did right in swapping the coil pack. Not much you can do until it reappears and it moves or doesn't.

 

Check the coil packs for any cracks on the body where it extends down to the spark plug. Cracks can allow the ignition pulse to escape out the sides of the coil and cause some weird shit to happen. Just something to look for with higher mileage on the coils. There are no plug wires to worry about.

This vid also might give you some ideas to look at - https://youtu.be/1bVC3AxGCgk

 

Interesting video, how do you fix it. New intake? New gasket? did he even repair it?

 

It's a 3 part video. I'm sure he did.

 

I will check it out, thanks.