30k/3yrs old Denso Double Platinum spark plugs - do I need new ones already?

[fenixus]

hey

Finally have gotten to inspect my V6's spark plugs ... at least in the front bank for now. Car has a history of broken AFR sensors circuit wiring, so it was running off the pre-defined fuel maps for (probably) good 2 years / 24k miles before I got.

here are pics of dealer installed Denso Double Platinum spark plugs (front bank, plugs from left to right for corresponding cylinders 2, 4, 6).

I have to say that ALL of those were not tightened properly! they required no effort at all to remove! for now I have just tightened them to specs (13ft-lbs), but I am actually worried about the gap.

Unless there is no good way to measure double electrode plug's gap with a coin style gauge (Autozone), then I'd say mine are too tight! all of them read around .035'' shouldn't it read .044''? perhaps I can't use this gauge on double electrode plugs?

pics:







Let me know if I need new ones yet or not, if yes then I replace all 6 of them with same model (I like OE style plugs), can get them cheap from Advance Auto Parts locally.

[garytho]

Boy,...I'd like to see the answers to this one too!!!!

[fenixus]

hopefully someone went down this path before and knows the answers, because I don't

[fenixus]

has anybody tried using regular coin-style gap gauge on double electrode plugs? any thoughts?

[TedL]

I've never found that type of gauge to be accurate enough to rely upon, at least not for my standards. I only rely on wire type spark plug gauges for gapping. I'll use the slide type to get an idea of how badly worn old plugs are before I toss them, but that's about it.

[ajkalian]

I think if you use the blade type gap tool you will get incorrect readings. IRRC the electrode has a recess cut into it to match the diameter of the center electrode. So by placing the blade across the gap you will get a reading from where the chord as defined by the outer electrode bisects the ends of the outer electrode. It might look something like the letter C and a vertical bar. maybe something like this: C|

Measuring the gap at either end of the "C" will give one reading, but measuring the gap at the center of the "C" will give another. I guess you could use one of the wire type gauges and orient the wire to be parallel to the electrode so you would get an even reading with reference to the electrode and the curved outer electrode.

Another thing to worry about. The coating on the electrode is very thin. Irridium, Shilirdium, whatever. So by rubbing the wire gauge in between the center and ground electrode you very well might be rubbing off the very material that gives the spark plug it's long life.

I'd just change them all out. The back ones aren't that hard. You just need skinny arms. Maybe your wife could lend a hand, or maybe an arm.

.

[fenixus]

yup there is a recess in middle. my idea is that side electrode (no matter what shape) distance from center ground should be equal (hence the recess), so at edges of "C" the distance to round center ground should read .044''?

anyways, I agree, coin style gauge is useless on those if inserted like I did.

I was very careful not to scratch off the horseshitium layer from electrodes car runs like before after re-install

seems I made a mistake measuring them like I did, should have measured edges of "C" to ground.

Originally Posted by ajkalian

I think if you use the blade type gap tool you will get incorrect readings. IRRC the electrode has a recess cut into it to match the diameter of the center electrode. So by placing the blade across the gap you will get a reading from where the chord as defined by the outer electrode bisects the ends of the outer electrode. It might look something like the letter C and a vertical bar. maybe something like this: C|

Measuring the gap at either end of the "C" will give one reading, but measuring the gap at the center of the "C" will give another. I guess you could use one of the wire type gauges and orient the wire to be parallel to the electrode so you would get an even reading with reference to the electrode and the curved outer electrode.

Another thing to worry about. The coating on the electrode is very thin. Irridium, Shilirdium, whatever. So by rubbing the wire gauge in between the center and ground electrode you very well might be rubbing off the very material that gives the spark plug it's long life.

I'd just change them all out. The back ones aren't that hard. You just need skinny arms. Maybe your wife could lend a hand, or maybe an arm.

.

the problem is shape of electrodes as ajkalian noticed. can't see that in pics, but there is a recess in middle of electrodes (to match the shape of round center ground).

i'd say this kind of gauge is useless for double electrode plugs, especially if you use it like I did in pics.

Originally Posted by TedL

I've never found that type of gauge to be accurate enough to rely upon, at least not for my standards. I only rely on wire type spark plug gauges for gapping. I'll use the slide type to get an idea of how badly worn old plugs are before I toss them, but that's about it.

do you think that besides the (wrong) measurement, plugs are OK or too dark from running rich(er) in past?

[71Corolla]

Those plugs will last 60k mile easily, 100k is about the point where they start to go south. I saw a Supra that had the original plugs for 220,000 miles, the gap was about twice what it was supposed to be, but the car still ran pretty good.

BTW, you can't accurately measure the gap, don't even try. Just trust that they are correct. NEVER gap them yourself, they are not designed to be gapped.

[MR2Jedi]

They look bad, sooty and carbonized, from what I can tell in the pics.
Platinums are good for around 60k miles, but 3 yr is a longtime to have them in, regardless.
I would change them and make sure you use some antiseize.
I prefer the individual blade type gauges to gap plugs.

[71Corolla]

Originally Posted by MR2Jedi

They look bad, sooty and carbonized, from what I can tell in the pics.

Really? To me they look pretty normal, most every plug I pull looks like that, slightly black. Those spark plug charts/pictures you see floating around are probably from the carbureted engine days, so the traditional colour some may be expecting doesn't really apply today.





.......spelled "carburated" wrong, ugh.

[pmesfun]

Original plugs on my car had about 130k on them and they looked just like the plugs in the pictures.

[MR2Jedi]

Maybe it's just this old computer, but they look really dark, like they are fouled with oil. Doesn't look clean burning.

[fenixus]

well, they should do 60k miles easily ... if car was maintained right all along (it wasn't before I got it).... so Idk, I think they are worn a tad too much...

I had somewhere pics of the very same plugs after 30k miles, pulled from 5s-fe and those looked much cleaner and better.

I believe driving with ECU AFR adjustment disabled for 24k miles sooted them a little too much, wasn't sure that's why I started this thread.

Yeah, I wasn't planning on re-gapping them, just was trying to see the actual gap, but it's not easy with double electrode plugs hehe.

Originally Posted by 71Corolla

Those plugs will last 60k mile easily, 100k is about the point where they start to go south. I saw a Supra that had the original plugs for 220,000 miles, the gap was about twice what it was supposed to be, but the car still ran pretty good.

BTW, you can't accurately measure the gap, don't even try. Just trust that they are correct. NEVER gap them yourself, they are not designed to be gapped.

That was my impression too. wanted a second opinion. I don't get the best mileage and recenty car feels a little weaker, so was wondering if maybe plugs have anything to do with it.
I guess I will swap them with new ones, those were abused.

Originally Posted by MR2Jedi

They look bad, sooty and carbonized, from what I can tell in the pics.
Platinums are good for around 60k miles, but 3 yr is a longtime to have them in, regardless.
I would change them and make sure you use some antiseize.
I prefer the individual blade type gauges to gap plugs.

well, I've seen a tad cleaner ones (from 5s-fe) after same mileage & time, same plugs model, here:

Old Picture from 2009 ... I think. I dumped those plugs to garbage when doing a minor tune up on 5s-fe back then.

I guess those on V6 call for replacement even more.

Originally Posted by 71Corolla

Really? To me they look pretty normal, most every plug I pull looks like that, slightly black. Those spark plug charts/pictures you see floating around are probably from the carbureted engine days, so the traditional colour some may be expecting doesn't really apply today.





.......spelled "carburated" wrong, ugh.

that pretty much means that in 30k miles my plugs got worn out like they did 130k miles...

Originally Posted by pmesfun

Original plugs on my car had about 130k on them and they looked just like the plugs in the pictures.

[fenixus]

yeah, they are kinda dark at the threads, also electrodes are oxidized/carbonized (dark grey looking).

just posted a pic of same type of plugs pulled out from 5s-fe after exactly same time and miles. those looked better.

I think former problems on V6 (AFR/o2 circuit fail) and driving with it for like 2 years (by prev owner) until I fixed it a year ago, was a little too much for them. car was probably running on richer side (felt stronger) until fixing the wiring problem.

I bet the rear bank plugs look even worse as that bank usually runs a tad richer when compared to front.

Probably will replace them next weekend for peace of mind, hopefully it improves the MPG as it still seems a tad low.

Originally Posted by MR2Jedi

Maybe it's just this old computer, but they look really dark, like they are fouled with oil. Doesn't look clean burning.

[Silent Runner]

I'd either clean them with a FI cleaner and a soft cloth. or replace them with something more familiar. Then again, maybe now that you have fixed the AFR issues, they can just be cleaned, and re-installed and the rear bank will clean itself up with some fuel additaves. Gapping a twin plug should best be left to guys with dyno's and exhaust analysers. May I suggest some Bosch Platnum 4's as potential replacements?