Autolite plugs - CHECK EM OFTEN
 

So I was looking at some Autolites that were barely 20k old on a DISI engine the other day, and while the tips looked good, something else caught my eye - The porcelain/plug part became internally disconnected/unsealed from within the threaded body. This means that exhaust gasses can squeeze by the plug from the combustion chamber and through the top of the plug into the coil/out of the valve cover. This affects - efficiency of combustion, connection of plug to coil (gasses push coil up and/or leave carbon deposits between plug and coil), and of course drive-ability. The plug in the vid was clean-ish looking because I wiped it off before making the vid. Other plugs had very large carbon deposits between the threaded part and the porcelain top part, you could see that exhaust was pushing out of there. I've never heard anyone have this type of problem, but they're cheap enough to replace every 10-15k so maybe not a huge deal, but def. something to be aware of.

Attached is a quick vid.

After multiple replies, I think we can all agree that we should - CHECK ANY PLUGS EVERY 15K MILES.
Btw, the stock heat NGK's come pre-gapped at .030-.032 ish so gapping them to 0.028 is really no extra stress on the electrode.

My opinion about autolite plugs = garbage. I'd throw in motorcraft/OEM Mazda plugs before that garbage. I've performed tune ups at the shop with them. Plugs go bad prematurely, even had one bad out of the box. I strictly stick with OEM/ NGK plugs. Never tried denso before..

Sorry I didn't watch the video, on the phone.

Fair enough... I have used and seen many other Autolites used with no bad consequences, as far as performance /efficiency / power go, but those shown above took the cake...

I literally just had a problem with an NGK plug this weekend. Fucking sucked dick.

I was getting break up at the top of pulls. Went to check my gap and one of my plug's porcelain part was cracked. With my luck; when I pulled the coil off, the pieces fell off the plug. So when the plug came out, guess where all of the pieces went...? Right into my combustion chamber.

Yup. That's how I spent my whole fucking Saturday... Trying to fish all that shit out - with very little success.

That actually happened to an NGK plug right in front of me to a friends car as well, we saw the porcelain cracked as we pulled it out, he was lucky that the porcelain didn't drop into the cylinder... sorry to hear it man, you may have to take the IM off and pressure blast those pieces out of the intake port. OR use those pickup tools, or a stick with some gum at the end, or double sided tape.

This is my worst fear ever. Now doubly so since you said its happened with NGK plugs. INB4 "now I have gum in my cylinder"

Pick up tool with gum stuck to it was my weapon of choice. LOL Grabbed the gum with the pick up tool and then wrapped it around the claws so it couldn't come off. Seemingly, I had no other option at the time other than to start that shit and hope for the best. Valve won, thankfully. I was scared for a minute though. Didn't want to do it but saw no other choice. I tried getting that shit all day before resulting to starting it.

Trying to line the pieces of the plug with the spark plug hole was next to impossible. Countless times I cranked the motor over with no coils plugged in, and every time they'd bounce out of sight.

If you ever run into that; I'd recommend trying a shop vac with a funnel. Didn't think of it at the time, but as we all know, hindsight is a motherfucker.

I can't remember the last time I left any set of plugs in this engine for even ~15K miles Anything over that is just losing performance and, apparently, asking for trouble.

The extreme angle that results from gapping autolites or NGK's down from .044 to .02x just wears em out too fast. Denso's will last a bit longer, but are just as likely to have failed ceramics as the other two.

My next plug change I'm gonna try a set of Brisk Racing plugs- heard nothing but good about them and have a set of their RR14YS Silver plugs at the house ready to get installed. These come out of the box gapped at .032 (will be installed at .026ish) and by heat range are comparable to ITV22's.
Brisk Silver Spark Plugs : Silver Racing RR14YS Spark Plug

As most of pointed out in the responses, this can happen to any plug.

Personally I think keeping plugs in for the recommended 75,000 miles is ludicrous. I rarely run mine past 20,000 miles.

Interesting news on the NGK's, I've always had good outcomes with those plugs. WHat do you guys think are the best plugs to run (non step colder)? (Don't mean to jack)

Does anyone run the Mazda OEM plugs? That's what I'm running right now without a blip.

If I told you the milage on the plugs I'd have to...51k :eek:

Before I tuned I gapped them and cleaned them (sand blasted). Have not had any issues per data logging and I constantly monitor like a fool.

They are being switched out next oil change though (I check them). Mazda recommends every 75k. Plus, it's time (obviously). I may just go with OEM's again because I have yet seen a speed have a faulty plug OEM. The coils on the other hand...

Mildly tuned the stock heat range are fine! I really only suggest going colder if you're +50 HP and driving reasonably hard.

Lotsa folks never take into account how much time they spend just cruising around, commuting or in traffic, and never really heating things up. In many cases it's actually better to have a set of track plugs that can be even two heat ranges colder, and a set of normal heat range, or one colder depending on your mods, for daily driving duties.

Honestly I tend to hear about the same level of spark plug reasoning as type of oil reasoning.
Denso and NGK both seem to be fine, Autolites tend to get a bad rap, yet I know more customers who call and say they are running autolites than the other two.... simply because they are cheap, without issue. Tons of people who run their car on the stock plugs for 75k miles without issue also. Honestly I don't think there is a wrong choice. lol. I always ran Stock or Autolite in mine.

I wonder if an air compressor could pressurize it enough to get the pieces to come out of the spark plug hole

I don't hold any hate towards the NGKs after my experience. I ran another set to 15k with no issue. To me, it was kind of a freak thing to happen; as I've never heard of that happening to someone.

Given how badly cracked my NGK was, I was amazed that it held up under normal use for a while until I checked them. I thought the first time it happened I had a weird fluke. Took 2 weeks for it to miss again. lol

Said bullshit. Really didn't capture it all though. It was split in multiple places all around the insulator.

I know you said you ran another set of NGK's for 15k, but how many miles were on this set that cracked?

I never even thought of this before. Scary, glad it worked out for you though.

Damn wtf that looks like defective. Plugs just don't do that.. I was thinking you meant around the electrode where it cracked.

Nope, I've seen them do just that. Porcelain is brittle.

And regarding the spinning issue above, 2 of the 4 Autolites did that.

I guess the real moral of the story is - CHECK ANY PLUGS EVERY 15K MILES. I'll put it in the top post.

I've had excellent luck with Autolites and NGK's, not so much with Denso. Denso's had chipped porcelain. I swap every 15k miles or so.

Yeah this thread is not as much about power/efficiency as it is about overall plug reliability. seems like regular maintenance/checkups are key, regardless of brand.

it's not like any of us have tried 1000 of each type of plug and can speak to porcelain cracking/tip erosion. to paraphrase a '90s phrase - check em early, check em often.

This was after maybe 8-9K miles.

Gap was starting to change, but it wasn't off by too much.

I have seen the ceramics crack on my own OEM plugs on my Gen 1. A missing problem had me yanking em at around 28K and the ceramics on 2 fell apart in my hands. #3 was cracked.

Never saw it on MS3 #2 (2010 Gen 2) Coulda just been a bad batch in the Gen 1.

I ran into issues with Autolite's. Two bad sets out of the box. On checking the element I found a flaw that seemed to be causing arcing at WOT right around 4K rpm. When I took the second bad set back I asked to look at a couple others on the shelf. They each had a bad plug in them. Switched back to ITV-22s that time and wow, no problems.

Recently did a new set of ITV-22s on the 2013 Gen 2. Really a well made plug, and out of the box they were perfectly gapped at .028. If you shop around for them, it is surprising how inexpensive they can be (under 8 bucks each).

BTW, the OEMs on the Gen 2 were perfect when I first yanked them at around 10K. I always keep the OEMs just in case.

I have just under 10k on my Autolites. I need to pull them and check them.