P0306 misfire code thrown via ODB...

Shyatic

Member
Any thoughts on what it might be? I've noticed the misfire, and my check engine light was blinking on some occasions. I'd love to fix it myself (if possible) so any thoughts here would be greatly appreciated!

Thanks!
 
Welcome to the forum.
First, can we have your vehicle information such as year & mileage?
If you have maybe close to around 100k, it could be a sparkplug?
 
I had the same code when i would go up an incline and accelerate and the light would be flashing. The dealer replaced the coil and plug. Code 306 which is the same code i got is for cylinder 6 which is easy because it is toward the rad. When you remove the engine cover you will see the 3 coils there.
 
Welcome to the forum.
First, can we have your vehicle information such as year & mileage?
If you have maybe close to around 100k, it could be a sparkplug?

I have a 2008 Mazda CX-9 Grand Touring, and I just broke 50k miles. I am reasonably mechanically inclined, so I can change the plug myself if that's it... or is it the coilpack? Can't really tell from the code, and I don't want to replace one thing and then have it be the other :)

Thanks!
 
That said... if it's the coil pack, where would I be able to buy that part online? I replaced a coilpack in my Audi years ago so I can't imagine it's too terribly difficult.
 
The front 3 are easy. Just pull off the engine cover. Don't even need tools, it just un-snaps.
The rear 3 require the intake manifold to come off since the engine is transversely mounted.

I don't know of a way to detemine if it's the coil or the plug other than replacing the plug and seeing if the problem goes away. If it does, then replace all the other plugs at that point.

One trick I know of to troubleshoot a coil is to run the engine (with the check engine light cleared), and use a very fine mister, and mist some water over each coil, see if you get any electrical arcing or rough running or check engine light comes on.

I know that on the old VW coilpacks, the plastic was manufactured too thinly, so it would develp very fine cracks that could not be seen. But in very cold damp weather, you could see arcing from the coil pack to the end of spark plug where it plugged into the coil pack.

So the misting method would basically be the same thing. But the coil might just be failing internally.

But again, other than trying to mist them, or replace the plugs, i dunnno how you would differentiate between the plug and the coil.

Good luck.

part prices would be best either on ebay, or possibly Jim Ellis Mazda online. Or maybe Rock Auto
 
Any thought on which is #6, so I can replace it correctly? I already got a new plug and coilpack, so just a matter of doing the work (which I don't think is too hard)... just want to make sure I get the right cylinder :)

Thanks!
 
#6 is in the front, the last one on front right! As stated previously, the fronts are quite easy, the rears take a little more time.
 

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