Mazda 6 Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
116 Posts
Discussion Starter #1
At 103,000 I replaced the stock spark plugs with iridium NGK’s.
I found this odd looking arc marks on all 4 below the stick coil boots. Possibly losing some energy? Super easy job BTW.

239518
142402D9-E09E-4F1F-A81D-C915894DD14E.jpeg
 

·
Registered
Joined
·
116 Posts
Discussion Starter #3
Can’t be oil, nothing showing below the ceramic. It feels almost like rust film. Maybe carbon? It scrapes off. The insides of the cylinder head wells where the boots are were totally clean.
Just weird....
 

·
Registered
Joined
·
189 Posts
Normal condition. Spark plugs exhibit characteristics generally similar to that after that many miles in service. The specific patterns in the carbon on that are neat!
 

·
Registered
Joined
·
116 Posts
Discussion Starter #5
Good to know. I’ve changed many a spark plug in vehicles and Motorcycles and never seen such a Carbon build up.
I checked the gap on the OEM plugs, they were spot on. The new plugs were off. No noticeable change in performance. Just needed to be done. Less than a 30 minute job. Cheers!
 

·
Registered
Joined
·
13 Posts
My guess is that you need to replace your plug wires. For the current to only cross that short path, it has to be coming down through the rubber that has given up it's insulating properties and then across the ceramic material to finish its path to ground. You would be losing some spark energy and I'm surprised that you would not have noticed a difference in power. I'm basing this on my experience in amateur radio tube radios with high voltage at the final power tubes and older tube type TV set. Sometimes a leakage path would develop inside the high voltage compartment (the HV "cage") and it could SOMETIMES be cleaned up and a spray coating applied to fix this. Sometimes you just had to give up on the old set.

I could almost guarantee if you replace the wires with new good quality silicone ones and replace the plugs, you will see this problem go away. If you get new wires and clean the plug ceramic material well, you MIGHT be able to reuse the plugs, but I would replace the plugs. And while there are many wild claims for all sorts of plug technologies, and some of those might last longer, the old type with a single bent electrode will give you no less noticeable power than the expensive ones. Get the expensive ones if you want plugs that will last longer. New wires are certainly in order with that many miles on them, so you won't be wasting your money and you might prevent a no-start condition on a very humid wet morning soon. You shouldn't see that happen again for about 75-100,000 miles.

It's possible if you can run the car in a very dark environment away from street lights on a humid night, you will see little sparks here and there about where you see the strange voltage trace marks, and probably also some little sparking along the outside of the wires.

If you want to get by cheap you can try to thorougly clean the outside of the wires and see if you can still buy a spray to coat the cables with something that will prevent current flow along the outside of them, and also clean your spark plugs, especially where you see those marks.
 

·
Registered
Joined
·
13 Posts
I only recently (very recently) acquired my 2014 Mazda 6 and haven't looked under the plastic guard over the engine yet (no need to yet but plan to do so when the weather breaks here to see the condition of the plugs, clean the engine, etc.). My 2005 and 2009 3 has ignition coils over the plugs, and I believe one coil served two plugs. Not sure of that though.

Glad you enjoyed my post. We need more humor right now and I'm glad to have served you a dose. :) I'll assume you're correct as that is the way things have been trending with ignition systems and I have no reason to disbelieve you.

This would then mean that the sleeve (or whatever you wish to call it) that goes over the top of the plug coming from the coil is dirty, possibly beyond what a good cleaning could fix. It's worth a try though.

The bottom line is that there is some light arcing across the ceramic of the plug and that means the HV is coming from the top part that goes over the plug, so there's likely a carbon trace now. If it's made anything like the older Mazda 3's I had, you won't be able to view the arcing because it will be hidden. That also means some of the current is being redirected through the leakage path. Whether that's enough to make a difference in power remains to be seen since we can’t drive it to make a judgment on it. I would start with a good cleaning since replacing the component isn't as cheap as replacing spark plug wires. Eventually this could lead to a miss and then one or more plugs won't fire if it gets bad enough.
 

·
Registered
Joined
·
13 Posts
BTW, this is my first 6 (I did have a 626) and loved it. It's the base model. If I were buying new I would probably buy the top level to get the collision avoidance features, GPS, etc. The reason I have this 2014 Mazda 6 is that I turned my head to look in the side view mirror, traffic ahead of me was a little close, and someone two cars ahead stopped suddenly, and I didn't have enough stopping distance (my fault), so the crash messed up the front end. It was driveable so I drove it home an hour away. Cost to repair was more than the car was worth (though I loved that Mazda 3). My first accident ever at 64 years of age, and I started driving at 16. Not a bad driving record, but it was a disappointment to say the least. I can now drive an hour to the big city and an hour to come home and not have my back wrecked. They did a great job of making this car ergonomic.
 
1 - 9 of 9 Posts
Top