Misfire on Cylinder 6, With Radio Inference After New Plugs

[OldSchool]

Hi. All apologies if this shows up more than once, I’m having trouble getting it to post and I’m not sure why.

I am working through a CEL that is throwing the 0306 code for misfires on Cylinder 6. This was intermittent about a month ago but the CEL has been on for 2-3 weeks now. I've got a JB4 on Map 2, intakes and cat back exhaust. The car as 49k miles and I've gone through two sets of the Denso plugs over those 49k miles.

Yesterday, I replaced all the plugs with the HKS plugs after gapping them to 0.022. I didn't see any cracking on the Denso but they were obviously worn after 25k miles. The code did not clear and I noticed a new observation as I was driving to work yesterday. The radio would intermittently cut out for about half a second. This wasn't happening prior to the HKS plugs going in and it got me thinking an intermittent, High Voltage, electrical discharge causing electromagnetic interference (e.g. coil pack). Went to Auto Zone, code producing only code 0306, so I ordered one OEM coil pack. Picked it up this morning. Installed it over lunch, on the cylinder closest to the steering wheel, and drove about 15 miles to work. Unfortunately, I'm still getting the code as well the intermittent electrical interference.

Another observation was made after installing the coil pack and before driving to work today. With the hood up and listening to the engine, there is a soft but constant ticking side coming in the vicinity of the intake manifold... around cylinder 3. I don't know if always been there or not, it could be normal, but I thought it was worth noting. Its related to the engine speed, but doesn't get louder with RPMS. My intuition is that it might be the fuel pump just doing its thing and I’ve never paid attention to it before. Can anyone confirm if they hear this type of noise on their car or not?

So any ideas on what to try next? It seems something specific to cylinder 6, not the plug or the coil pack. I’ve also disconnected the JB4 and that hasn’t impacted the misfiring or radio interference.

Thanks for the advice.

David

 

[rk88]

Did you check the fuse box to make sure nothing looked loose or broken?

 

[OldSchool]

Update. I swapped the plugs and coil from cylinders 6 and 4. CEL went out and the car is driving like normal. Wasn’t expecting that to fix it! No idea what transpired.

 

[Snicklefritz]

Now that would just make me nervous. It can't be a permanent fix, can it?

 

[Alpinesting]

You are correct about the fuel pump noise. The coil packs however are funny and most of the time will

not trigger a CEL and will cause audio dropouts in the entertainment system. There are telltale signs on

the coil pack boot that will show that voltage is leaking. I have some experience with this and it was

a real issue with the oem coil packs pre 2022. If you let them go they will foul the plug and give a CEL.

Having said that, those two marks that are yellowish are a sign that the boot is leaking voltage and this

can be intermittent thus causing the audio drop outs. Just my experience on the matter. They make

far better boots now for the coil packs now so maybe check that out. I would also get a code reader

that is a little better than the ones at the auto part stores. If it were me and you have the tools, pull out

your coil packs and give them a look or just replace all of them with newer OEM or aftermarket coil packs

before you foul another plug.

 

[OldSchool]

Alpinesting,

Thanks for the reply. It’s timely because while the car is driving well and the light is still off, I am still getting some intermittent audio dropouts. Maybe not as much, not sure. I

will inspect the original coil pack that I removed for any yellowing but I suspect the primary offender is still in the engine. Expensive but I may just buy 5 more of the new packs and be done with it.

 

[Alpinesting]

Alpinesting,

Thanks for the reply. It’s timely because while the car is driving well and the light is still off, I am still getting some intermittent audio dropouts. Maybe not as much, not sure. I

will inspect the original coil pack that I removed for any yellowing but I suspect the primary offender is still in the engine. Expensive but I may just buy 5 more of the new packs and be done with it.

Happy to help. Agreed, I am sure that there is another one leaking. You will get it sorted out.