Brown Ring of Death - Learn from my $400 lesson

[Gearhead]

My M60 has been running increasingly rough at idle for the last few months. It does just fine off idle and through the power range, but at idle it had that intermittent misfire very much pointing to an ignition problem. Being that I just installed a new set of NGK plugs and coil to plug connectors about 6 months ago, I doubted they were the cause, but I yanked them anyway to check. I ohm tested them and they all were fine...none with too much resistance. That said, I did notice an interesting brown ring on 4 of the 8, there on the ceramic right where it meets the metal/hex case. Didn't think much of it.

So, I'm now ohm testing the coils when cold and again when hot looking for anything out of norm. Nothing. Then I read a post about how a coil can pass the primary winding ohm test, but still fail and how you need some di-electric tester to make sure. yeah...I don't have one of those in my tool box.

Anyway, just about at that point I start getting a CEL, code 1212. Ha! O2 sensors....that MUST be it. Nope. $230 later the car is running better through the power band, no more CEL, but the rough idle remains.

Now I'm pissed. I figure, okay, I'll buy 4 ignition coils and chase down the misfire by playing musical chairs under the hood. Well, I thought about it for a while and realized i was still guessing, so I might as well drop the $85 on a diagnostic test and at least be sure of the issue.

The test showed 4 of the 8 cylinders misfiring. Guess which ones? Yup, every one of the four with that BROD (Brown Ring of Death) on the the plugs. According to this shop owner (he's a former Electrical Engineer and is from Bavaria, Germany), some plugs are prone to electrical leaking at this ceramic/metal case junction. The tell-tale sign being the BROD. 8 new BOSCH plugs and another $200 later (I just let him do the job) she's purring at idle again.

Had I known this before, I could have saved a bunch of time and cash. And I still have to wonder if the O2 sensor failure was related to these plugs puking. Anyway, learn from my ordeal!

Best and Happy Holidays!

John

[632 Regal]

Wow, I wonder... think I know what I will be checking on my little holiday!

[Qube]

Nice, thanks for posting this info.

[Dave M]

Thats a new one for me, thanks for posting. If you provide the NGK part #, maybe we can play CSI (Car Stumbles at Idle).

Dave M

[winfred]

actually just about all of the plugs i change have the rust ring around them even when they are just old, i ohm test them against the rest of the set and check that theres no connection to the ground part of the plug, seen a few some of them fairly new short to ground

[ThoreauHD]

As an alternative. The denso iridium's that I have have been error free since I've owned the car. Guess that's about 2 years now. If you find it happening again, you might want to give those plugs a look. I also think NGK has iridiums out now, but I haven't used them so I can't speak about their durability.

[Ferret]

Some thoughts about this...

When I bought the 540i a couple of months ago, it had two shot plugs in it, so I changed the lot for a set of cheapo NGK type 'R' plugs.

Over the christmas period, I left the 5er stood for a week while off visiting far flung family - came back and the car had a massive misfire. The car had gone into a deep freeze while I was away, in constant shadow and down to -6C temps - it took a good hour to defrost the frozen lump. After running it around for a couple of days the misfire had all but disappeared.

Out of curiosity I pulled all the plugs and found 7 out of the 8 had this 'brown ring of death' around them. The only one that didnt have it was the set that had the brand new coilpack to plug lead - original bmw part.

After taking a sharp knife to the offending brown parts and having a scratch around, it appears that the arcing is either creating a new coating or slowly eating the ceramic. Bearing in mind the plugs are only 2-3 months old, the level of corosion on them was amazing.

I'd have to guess this is something to do with condensation forming on the plugs, combined with arcing is causing the plugs to degrade rapidly. I'll be off to bmw shortly to grab a set of new coilpack leads before I fit the new bosch plugs I picked up this week.

I suspect the v8 misfire problem is more to do with the lead condition than the plugs, but the NGK plugs do seem prone to this kind of behaviour...

[Gearhead]

Some great feedback Ferret. In my case, all my leads were less than 6 months old and still in "new" shape. All the plugs were the same age, but only 4 of the 8 had the BROD. They were the NGK BKR6EK plugs. Also, it hasn't gotten that cold down here in Florida.

So you're thinking condensation? Hmmmm....

[Jon K]

As an alternative. The denso iridium's that I have have been error free since I've owned the car. Guess that's about 2 years now. If you find it happening again, you might want to give those plugs a look. I also think NGK has iridiums out now, but I haven't used them so I can't speak about their durability.

Iridium is a waste of over $65. Do not waste that kind of money on spark plugs, there is no point. NGK BKR6E for $1.70 @ Advanced Auto will do you wonders. NGK makes a quality plug.

[whiskychaser]

Owned a fair few cars over the years and found this occurs on all the makes of car I own. So maybe its geographical? While I clean it off with white spirit (or pan scourer!) as I dont think it looks healthy, I havent suffered with misfires all these years. So whats causes it? Baked oil mist? (and for the germans looking in, yes we know what mist means!)