What do these spark plugs tell you?
 

Hey guys, pulled my spark plugs to do a compression test today (all put out 180psi +/- 5psi). I noticed that my cylinder 2 spark plug was completely different looking from the rest. I read online some about reading spark plugs, but I am not too confident in my conclusion here.

-I had some oil on cylinder 1,3, and 4's threads. and all 4 had some oil residue on the outside porcelain. So I am getting some blow-by??
-The coloring implies I am running ok, but perhaps a little lean or too hot on cylinder two as the white is too far back on the ground strap. I also have that peeling on the porcelain on cylinder two.

Plugs where on for about 10k miles. What the fuck is up with my cylinder 2 plug? and what can you tell more about how my engine is doing?

Mods: minimal here, just full exhaust.

have a looksy guys:
Cylinder 1:
http://www.miataforumz.com/attachmen...ine=1318287188
http://www.miataforumz.com/attachmen...ine=1318287188

Cylinder 2:
http://www.miataforumz.com/attachmen...ine=1318287188
http://www.miataforumz.com/attachmen...ine=1318287188

Cylinder 3:
http://www.miataforumz.com/attachmen...ine=1318287188
http://www.miataforumz.com/attachmen...ine=1318287188

Cylinder 4:
http://www.miataforumz.com/attachmen...ine=1318287188
http://www.miataforumz.com/attachmen...ine=1318287188

Group pic.:
http://www.miataforumz.com/attachmen...ine=1318287188

I would like to know the answer as well since I'm in the same boat.

Found it interesting that you are concerned about #2, but those were the worst pictures.

From what I can tell, these look like normal deposits. I would like a better picture of #2 though. #2 may be running a bit richer than the others.

The oil on the outside of the plugs means that your valve cover gasket could use replacing. It is leaking a bit.

Oil on the outside of the plug and on the threads is generally due to a leaking valve cover gasket. Unfortunately, due to all of the additives in today's gasoline, you can't really 'read' plugs the same way the old timers did back in the day when men were men and gasoline was the purified blood of our enemies.
If you start seeing "salt and pepper" though, that is a good indicator of detonation.

I can't wait until you post your for-sale thread. I'm going to go out of my way to rape you in the fucking e-face.

Yea Cylinder 2 was the first set of pictures I took. The VC leak...I have had this VC for a little under 8k miles. Its never really sealed well, even though its the OEM one. I think I have it sealing now, atleast when I feel the plug holes there is no wetness in there. I will probably replace these plugs, just so I can keep track of it. plus these have a good 1000+ miles on track.

Here is a few more of Cylinder 2 spark plug...I have uploaded them to my FTP server, so you can get high quality images. I have to say IMAG401/402 look a bit scary, not sure if its specs of metal or just deposits (I think its deposits, but the paranoid freak in me says its not)...

Server Link
Username: Track
Password: frogwheelslurp

https://www.miataturbo.net/attachmen...ine=1318294545

https://www.miataturbo.net/attachmen...ine=1318294545

https://www.miataturbo.net/attachmen...ine=1318294545

so...I went out and while the plugs were out, I soaked a paper towel in seafoam and swiped up all the cylinders. I had a lot of black gunk/shit come out on cylinder 2 and small metal specks in it. :( :( what the fuck is causing cylinder 2 to detonate?? :(

Would this be due to the spark plug itself? what are possible culprits, I have two track days coming up in two weeks and this is NOT good news at all. Wait...a minute, I think I got an idea here...

ok, so I think the metal specs are left over from anti-seize that was used on the threads a while ago. I confirmed it by checking the grime on the piston itself, which came up with nothing more than carbon deposits and no specks of metal. Anyways, if anyone else can give me more info on cylinder 2, that would be greatly appreciated!

Well, it's nice to know my engine is healthy, lol.

lol, I hope your valves are fucked. :fawk:

They all look pretty lean if you ask me. Also, seems like your timing is a little too retarded and I'll bet that gap is .35-40in when you should be closer to .25-.30in

I like to see a nice even black ring on the very end of the body, but not on the threads themselves and spark wear on the middle of the ground electrode.

Can you hear any knocking when under load? What brand/heat range plugs?

NGK stocks. copper I think its BKR5 (you can see it on one of the plugs).

btw, I forgot about htis, I do have the MSM cams installed (among my 01+ header and 2.25" exhaust). I have a scangauge and run about 8-11 ign timing on idle. I think when crusing on the highway at about 4k rpm in 5th I am anywhere between 30-40 on the timing.

I agree about the lean, I have been reading more about this and I am concerned that its a combination of a weak fuel pump and/or clogged filter + MSM cams. I don't think I have a vacuum leak as I did a vacuum test and got 20.5 in at idle. I will say my P0402 (excessive EGR flow) keeps coming on. and was NEVER P0401 like what is commonly seen (according to m.net).

Oh, I don't know if its knocking (sorry I am a newbie to engine sounds here, but I am learning), but on the occasional hot day, if I park my car for about 10-20 minutes when I start it up I will hear a tapping/knocking noise in the rpm range of 1k-1.5k. it goes away after a minute of driving.

This is a turbo car correct? Better yet, what year, engine management, etc?

No, its not. No FI yet, although I am lurking to learn. Stock ecu. everything is stock except a hacked out interior, seats, the MSM cam, and the exhaust.

like I said, I think I used anti-seize on these threads. so its possible the grime on some is from that. and yes, I did have some oil leaking into the plugs. god this is a fucking mess. So what do you think about the theory here with the fuel pressure or filter? ( replaced the filter last year, or about 15k miles ago). I might run some chevron through it, incase the injectors are clogged.

Well, the fact that it's not a turbo changes everything. I remember my stock miata ran lean at cruise on the lc1, like 15.0-15.5afr.


If it's running ok, I'd leave it alone or just buy new plugs (they're cheap) and gap them correctly, .45in I think for stock. If you do indeed have a stuck egr valve that can create a lean condition. Is the egr tube still connected with the new header? Connector for the valve plugged in?

what about the chipping porcelain on cylinder 2? 99 manual says 1-1.1 (.04-.043in).

I think they are a bit off, probably eroded some from use. I have a new set waiting to get installed when I drive it again.

yea ok, so freaking out is over with. after some more reading and pictures taken without an LED flash, I think the "cracks" on cylinder 2 are actually deposits from oil leaking in from my valves. The car has been consuming oil (hence why I am doing a compression and leakdown test) and from reading more about it, a few websites provide some good info:
"ash deposits"
http://dodgeram.info/Engine-Gas/Spar...plghnbook.html
http://www.spark-plugs.co.uk/pages/t.../diagnosis.htm

Anyways, thats good to hear really. I will do the leakdown test after CMP, but I am still going to run some cleaning on her before friday. I will update with leakdown results which should identify if its valve seats or valve seals/guides.

here the pictures for any interested parties:
https://www.miataturbo.net/attachmen...ine=1318390481
https://www.miataturbo.net/attachmen...ine=1318390481

Those are definitely deposits, not chipping. Nothing to worry about. Press ahead.

dude your plugs look just fine. don't worry about anything. i have seen some UGLY plugs in my short time wrenching. Yours are happy.

Thus spaketh zarthrusthra

haha yea, thanks guys. Good to know others share the same opinion. I will just have to keep a watch over the plugs every 10k miles or so to make sure they don't get too much deposits on them. I will fix the valve seals sometime later this year.