Rear plugs

Front plugs

Good day all,

I recently took the 8 out of winter storage and went through a tank of gas already and noticed slight rough idling once warmed up and thought since it’s been about 2 years since I changed plugs it might be time.

So I pulled the plugs to look at them. They’re fairly black and one has some visible carbon chunks in the grooves, but strangely, the front trailing plug looks much cleaner than the others and was slightly wet (not sure if it was oil or gas).

What could this mean? I should also mention the car came with Napol yellow coil packs and Napol plug wires...no idea of those are good or junk. Probably going to get a set of the BHR globally compliant coils either way.

For now I’ll clean these up and run them until I get a chance to pick up a new set.

Thanks!

 

Front trailing plug might not be firing properly.... the electrode is pretty dark.

Does it idle like crap?

 

The idle once up to temperature is a bit rough. It would stumble and I can hear frequent pops in the exhaust.

 

Possible it was bottomed out in the slot? What does the slot it came from look like, inside?
What's weird is the carbon on the electrode has a sharp cut off, which makes me think that for some reason the outer portion of the plug was not exposed to fuel-air mixture (and/or wasn't firing properly). Also the innermost edge of the outer portion looks a little compressed compared to the other plug.

Did this car spend a lot of time idling? That's a lot of black deposits, like it ran rich.

 

I agree with Dan; looks to me like the cleaner one isn’t firing properly. Notice that on the others the sparking surface on the round electrode tips are bright and shiny for their entire diameter, but not on the cleaner one. Not going to get any build up if it’s not firing. Probably need to load test and/or just replace the coils and spark wires. i’m of the opinion that those china ebay coils are most likely junk. That wouldn’t be doing the catalytic exhaust converter any favors either.

 

I’ve never heard of the plug bottoming out in the hole, I thought the thread length would take that into account?

In my opinion it seems to be running rich, since I noticed a decline in fuel economy I’ve the past two summers. Two summers ago it would get 11.5-13 L/100km regularly (hwy/city 60/40), now it’s more like 13-14.5.

Well I think I’ll just order up some BHRs and some new plug wires and go from there. The plugs themselves, aside from being dirty, still look decent to me.

 

Good plan. It'll definitely use more fuel if some of it isn't being ignited
don't drive it like this, it'll kill your cat.

 

Well I’ve got a brand new RB resonated midpipe in the garage waiting to be installed, so the cat is coming out soon anyway.

 

Before...

...and after.

So I got my BHR coils installed and immediately I noticed some things. Hot starts are noticeably quicker and the idle stumble is gone. Will continue to monitor the performance this summer, specifically the fuel mileage.

Anyone have any experience with these yellow Napol (NP) performance coils? To me they just look like OEMs in a yellow case.

 

throw them in the trash where they belong …
.

 

Thats basically what I was thinking anyway.