So I was getting random intermittent pops and backfires, and even though my plugs had just been replaced when I installed a full BHR ignition kit about 10k miles ago (barely a year now), they are often the first culprit and easy/cheap to replace. Upon replacing the plugs, which should have been fine, I found them rather heavily fouled. Additionally, upon removing the rear Leading plug, the tip came loose and the whole central core came out, looking like it had been burned, corroded, and half-melted, as per the attached pic... Obviously the car is running much smoother now with brand new plugs, but what could have caused this kind of severe damage in barely 10k miles? Anyone seen this before?

 

I think in othrr threads where the element has snapped , ngk have replaced them

 

The one trailing plug in that picture hasn't been firing either..the electrode is totally fouled up on the end. So basically you had 2 out of 4 plugs that look like they are working.

Replace the plugs and see if it runs better...you might need to check the trailing coil that was firing that plug....

 

My limited experience is it also doesn't help that many of us are tightening those plugs from a fair distance away that leads to damaging torque on the plug heads. I've gone to checking current and installing new closer up by removing the front tire and working close to the point of attachment (and hand threading on or after loosening hand threading off those plugs).

 

Both good points, it doesn't take much to damage them. I do my final torquing as close as I can and only go hand tight as I have seen a few people break them. I have never had an issue and I change mine yearly.

 

i cracked a plug once the first time i did my ignition. it was arcing against the block and giving me misfires

 

Yes, I actually bought one of the T-wrench style spark plug socket wrenches online just for this exact purpose the first time I changed the plugs (about 2 years ago). It has the flexing double U-joint and the rubber interior, so I don't think it was my actions that broke off the tip/core - plus, that core was severely melted/corroded/damaged either way.

Also, dannobre, how would I go about checking my coils for spark functionality? Or is this a thing that a shop would need to do on a rotary? (I remember when I had an old 4cyl Ford Contour with a little easily-accessed distributor unit I could simply unplug one of the wires from the distributor side and touch something metal and it would spark if it was good, but I'm guessing that's obviously not the case on a rotary).

They're BHR so they should have a lifetime warranty if I remember right..? So if one is dead I should be able to get a new set? I haven't actually looked at that recently though, so I could be wrong on that.

 

Checking for proper spark is easy, there is a DIY here for testing the D585 coils specifically.

 

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I recently had a same type of problem/experience and contacted the HQ of NGK in Germany.
My experience with NGK therewith was rather bad and I am not satisfied at all with their handling of the problem.....of course they answered me.....but doubted if I had used the right type of sparkplug......which was stupid since they could identify the type of plug by the pictures I did send.........in another part of their reply they gave me an advise for the right type of plug, which advice was the same as the types I used.......
They ended the letter with an advise to contact my sparkplug supplier, so he could judge the damage and could take eventual action towards NGK.
In praxis this is rather difficult since I bougt a couple of NGK plugs at Zapparts, Mazmart, in the UK etc. and this way is to complicated to me, also due to difficulty of communication.
With all those worlwide selling channels incl. eBay and Amazon I am of opinion that NGK should anticipate on that globalisation and should offer the opportunity to their customers to deal in case of problems directly with the enduser.


If you are interested in more details about this, undermentioned find what I wrote to NGK-Europe-HQ in Germany..................

Dear Madam, Sir,
I am the owner of a MAZDA RENESIS RX-8 HP WITH ROTARY ENGINE (231hp) of 2008 (VIN nr. JMZSE173650121340); purchased new; now 57.000 kms on the odometer. My exhaust tips were always very clean / hardly no carbon deposits in/on the tips (I premix synth. oil 1:250 since new)....however since the tips became slightly blackish on the inside I immediately had doubts about the ignition system; expecting the ignition coils (49.000 km) as the problem. However they were ok/excellent, but by renewing the coils, leads and plugs (all after a running period of 49.000 km) I noticed that on the 2nd rotor (closest to the firewall), after popping of the leads, from both Leading and trailing sparkplugs the inner core was broken and left in the leads. Before disassembling the ignition system the performance of the engine both at high rpm and idling was excellent. This is a dangerous situation as it can damage the catalysator and also the engine. In my opinion the broken core's caused the combustion not to be proper/efficient for the last 1.000-1.500 km's. My problem is that the NGK spark plugs-types adapted are exact conform the requirements both of Mazda and NGK Both sparkpugs broke down at 49.000 km which is within the 60.000 km replacement interval Mazda requires. SOME DATA ABOUT MY DRIVING CONDITIONS: * Generally medium distances from 50-150 km (one way); never less than 5 kms; sometimes 20 kms; no high rev's during warming up to 80 degr. C (I have an engine sump oil temp meter) * Sump oil temp. 90-95 (max. 100 in peak hour traffic) degrees C in summer; 85 degrees C in spring and autumn; in winter the car is not used. * Engine oil synthetic 5W30/5w40 * Moderate drive style; never to low in gears; never the high rev's of 8.000 rpm etc. (I am 73 years of age but also have a Lotus Esprit Turbo SE and a Classic Saab 900c) * I am very cautious with this fantastic RX-8 HP and when (dis)mounting the spark plugs I always pay utmost attention to "hand screw in" and caring not to hit the porcelain isolator. I HAVE ENCLOSED 7 LINKS OF PICTURES OF THE DAMAGED SPARK PLUGS. Please advice what to do; was this only a unlucky event (which I could accept immediately) or is there some other reason. Please eventually consult your Japanese collegues of NGK as they have a broad experience and knowledge (of problems) with the Rotary Engine of the MAZDA RX-8
Note: the spark plugs were not stressed by "towing leads".....they were attached flexible.
Best regards, Rudolph Wolven


This was the reply of NGK after couple of days (Dutch translated to English by Google-translate)

Dear Sir Wolven
Thank you for your message. We regret the situation that you have described in great detail.
We can not and must not, however, on the basis of these data and the you that was sent pictures give a ruling on the cause.
If your vehicle data matches the data below, the correct spark plugs for your car are: RE8C-L + RE9B-T.
If the correct spark plugs are used, may be examined at the technical center of NGK spark plugs, to assess whether they have functioned properly.
For this you can spark plugs including offering your report / report at the store where you purchased the corresponding spark plugs.

The point of sale the spark plugs with the necessary forms can be sent directly to NDA.
Once the investigation is completed there will be prepared a report and sent to you.

PS: Because of your interest in technique we refer you to our new technical platform: http://www.tekniwiki.com
On this new site you will find a lot of technical information tips.

With best regards / Mit freundlichen Gruessen / Sincerely,

KCC department (Customer Contact Center)
NGK Spark Plug Europe GmbH
Geschaeftsfuehrer / Managing Director: Masaki Sumiya
Harkortstr. 41, 40880 Ratingen, Germany
AG Duesseldorf HRB 43118
Website: http://www.ngkntk.de


My reply on the anwer/conclusion from NGK........

Dear "Afdeling KCC (Klant Contact Center)",
Thanks for your quick reply, however it is disappointing and not of great help for me since it more or less reads like "a standard reply with very few and irrelevant commitment".
It is in my opinion considered as irrelevant commitment because you said........"If the right type of sparkplugs are used,"........whereas from my pictures you could clearly see that I used the right types of NGK spark plugs.
Your reply furthermore is not very practical since I generally purchase my NGK spark plugs via internet in the USA or UK and (still having 2 more sets of spark plugs in store) do not know exactly where/when I ordered these specific plugs in the USA/UK.
Furthermore I can not understand why these faulty plugs have to be sent to you via an extra intermediate link/dealer (causing misunderstanding / evt.missing shipments and unnecessary extra costs) and can not be send to you directly for judgement.
On the basis of your unusable reply I will leave the problem as it is.
However on a short notice I will publish the matter of the broken NGK spark plugs on the international RX-8 owners forums in the USA, UK, Germany and the Netherlands (which I all frequently vist and post as a member) as a serious warning since this kind of damage with the spark plugs , in the case of the Rotary Engines of the RX-8 (not with 4 stroke engines) principally always cause a total catalysator and engine failure on a short term with total repair costs of approx. Euro 10.000,-.
My fellow RX-8 owners need to be aware of this hidden catastrophic danger.
Best regards,
Rudolph Wolven

 

I wonder if my "bad gas" I got from that Shell station is warranted and they'll reimburse me for my bad cat service by that dealer?