What is destroying sparkplugs in my engine?

[tortillasoup]

OP, if the owner's manual and the shops are saying to use a specific spark plug, USE THAT PLUG. END OF STORY. I don't care if your spark plugs were stamped with a "blessed by Jesus" sticker, they're obviously the wrong spark plugs! You're using too hot of a spark plug as indicated by everybody on here, put the plugs the car is suppose to come with according to the owner's manual/service manual/every website in existence says and then come back to us if and when you continue to experience this problem.


This is a colossal waste of time arguing over this.

 

[LTC8K6]

Plugs that were too hot would all look like #4.

It's only #4 that has a problem.

So I think it's safe to say the problem is not the plugs.

And I think we have covered all of the likely scenarios here pretty well.

It's up to the OP or his mechanic now.

 

[boomerang]

Would the heat completely remove the side electrode at the weld/braze in 500 miles though?

That's a good point too. Seems awfully quick. It's frustrating isn't it? You just want to be on site and looking at things and all we have are good pictures, but not necessarily the best view of what we want to see. I'd really like to have one of those plugs in my hand to inspect the weld point of the side electrode. I'd really like to have a look down that plug well with a plug removed. I'd also like to see if I could get a good view at the top of the piston.

This is one for which I'm really interested in hearing the outcome.

 

[tortillasoup]

The plugs are the incorrect ones for the vehicle. What the op got away with for whatever duration is irrelevant at this point. If OP wants to be a cheap ass, he can purchase a single spark plug that is the correct one, put it in and see if the electrode breaks off... What I think will happen is that OP will find a cylinder misfire in a different cylinder when that spark plug electrode then breaks off because it's the wrong plug for the car. Op will hopefully realize he was wrong and just replace all of the wrong plugs on the car with the correct ones.

 

[LTC8K6]

The plugs are the incorrect ones for the vehicle. What the op got away with for whatever duration is irrelevant at this point. If OP wants to be a cheap ass, he can purchase a single spark plug that is the correct one, put it in and see if the electrode breaks off... What I think will happen is that OP will find a cylinder misfire in a different cylinder when that spark plug electrode then breaks off because it's the wrong plug for the car. Op will hopefully realize he was wrong and just replace all of the wrong plugs on the car with the correct ones.

I see what you are saying. Is the heat range difference really that great between the 5 and 6 versions of the plug? It's one step, right?

ITR5F-13 / ITR6F-13

It's always plug #4, according to the OP. No mention of any other plug looking bad.

this is the THIRD sparkplug in that same cylinder (#4) that lost it's tip in 50k miles.

all the gaps are factory.

 

[tortillasoup]

The heat range difference is enough to give it a different number so yes I'd say it's a big enough difference. Plug gets too hot and since it's an iridium tip, that's the last thing to fail on the plug with that brazed electrode likely the first thing to fail.

 

[LTC8K6]

L303 18 110

Part number in the manual. That's what he has in the engine.

http://ryanlabarre.com/images/axela/plugs/1.jpg

 

[tortillasoup]

I just looked up the 2005 Mazda 3 and all of the engine configurations use ITR6F13 or a derivative with that "6" heat range. The plugs have a .052" gap which is already quite large and I'm sure they choose that gap for best fuel economy but at the cost of running hotter.

 

[boomerang]

I just looked up the 2005 Mazda 3 and all of the engine configurations use ITR6F13 or a derivative with that "6" heat range. The plugs have a .052" gap which is already quite large and I'm sure they choose that gap for best fuel economy but at the cost of running hotter.

Remember that it's only one cylinder and that cylinder shows carbon buildup in the plug tube. Regardless, it appears that Mazda made a change in the heat range they wanted his engine to use. He should use what's now recommended which is a colder plug.

In researching NGK heat ranges I ran across this which shows how a spark plug dissipates its heat. One can see the importance of having a properly tightened spark plug with full seat contact.

 

[SparkyJJO]

If Mazda realized that one cylinder ran hotter, and a one step colder plug fixed the potential issue, and the colder plugs in the other 3 cylinders didn't negatively effect anything, then yes, they could have easily changed it to calling for a step colder plug across the board to fix one overly hot cylinder.

Yes this is just a guess, BUT if there is something I've learned it is to never assume anything and check everything.

 

[LTC8K6]

It was already posted that many sources list the 6 version as the correct plug.

I wasn't able to find any confirmation that Mazda changed the plug spec from 5 to 6.

 

[LTC8K6]

http://forums.anandtech.com/showpost.php?p=32918814&postcount=1

He appears to have already tried a 6 range plug. And swapped out plugs a couple times.

Didn't mention a missing electrode on #4 ITR5F13 when he removed them. Old or new. Or on the 6 range plugs he tried.

 

[tortillasoup]

There is actually a very simple explanation to all of this... 1. The gap on the original spark plug was wider, leading to better MPG. It wasn't fouled so there wasn't a need to replace them, therefore having good fuel economy. 2. He switched to the correct plug and got slightly worse MPG because the gap is now smaller but correct. 3. Because he sees an MPG drop going to the new but correct plug so he switches to a new but incorrect plug like he had in the car in the first place and sees even worse MPG.

So did OP stick in his old plugs? Who knows!? But what we do know is that he's got the wrong plugs for that car and he should use the correct temperature range plugs and go from there.

Plug temperature is a compromise between allowing the plugs to get hot enough to self clean and having the plugs destroy themselves from running too hot. In the case of OP, the plug(s) are destroying themselves for what ever reason and so the only solution is to switch to a colder and correct plug for his vehicle.

 

[LTC8K6]

There is actually a very simple explanation to all of this... 1. The gap on the original spark plug was wider, leading to better MPG. It wasn't fouled so there wasn't a need to replace them, therefore having good fuel economy. 2. He switched to the correct plug and got slightly worse MPG because the gap is now smaller but correct. 3. Because he sees an MPG drop going to the new but correct plug so he switches to a new but incorrect plug like he had in the car in the first place and sees even worse MPG.

So did OP stick in his old plugs? Who knows!? But what we do know is that he's got the wrong plugs for that car and he should use the correct temperature range plugs and go from there.

Plug temperature is a compromise between allowing the plugs to get hot enough to self clean and having the plugs destroy themselves from running too hot. In the case of OP, the plug(s) are destroying themselves for what ever reason and so the only solution is to switch to a colder and correct plug for his vehicle.

So, why wasn't the electrode missing from #4 at the time of that post?

Those factory original ITR5F13 plugs had been in for a while. How did the wrong plugs last 80k miles?

Plus he briefly tried a new set of ITR5F13 plugs at that time. Neither appears to have had a #4 lose an electrode.

Yet later he loses 3 #4 electrodes in 50K miles with ITR5F13 plugs? One of them in just 500 miles.

Do you think maybe there has been a little too much plug swapping?

 

[tortillasoup]

It's a logical fallacy to believe that just because something has never happened before, it can never happen. I don't need to "figure out" why such and such didn't happen, fact of the matter is, he is suppose to use a colder spark plug. It's totally irrelevant at this point about why he was able to get away with using a hotter plug, fact of the matter is, everybody is calling for a colder plug and this spark plug is being damaged being it's getting too hot in the cylinder. Why the other plugs aren't failing as well is because things don't just magically fail all at once. I'm sure eventually the other plugs will experience this issue if given enough time. Maybe he's got carbon build up, maybe there is excess EGR running to that cylinder and only that cylinder maybe he's got a clogged fuel injector and the cylinder is running slightly lean, therefore running hotter than when run at 14.7:1 or less.

I don't know if OP is installing these plugs in a hot or cold engine but he needs to know that you should always install the plugs when the engine is stone cold. OP should buy the correct plugs and get a torque wrench and replace with the correct ones. End of story.

 

[LTC8K6]

If it came with those plugs, and ran fine with those plugs for most of it's life, and the owner's manual says to use those plugs, how did they get to be the wrong plugs?

Looking around the net it's clear that those are the factory plugs.

If there was a change by Mazda, I haven't seen documentation of it.

 

[LTC8K6]

Not sure why I care anymore but the 6 series plug seems to be for Mazdaspeed engines but it works okay in the regular engines. One fellow said Mazda changed it early in the build year to the 6 series plug.

For reference, even in the 2006 Mazda 3, the factory plug is a 5 series plug, according to the manual.

LFG1 18 110
ILTR5A13G

Same for 2007 with the regular engine.

For 2007 we also have a turbo engine option, and that uses a 6 series plug.

L3K9 18 110A
ILTR6A8G

 

[JEDI]

IIRC, this one occurred after only 500 miles on new plugs.

My understanding is that new plugs were installed. At 500 miles the code came up. Plugs were pulled. Electrode is already missing.

We don't know when the previous one occurred in the life of the plug, iirc. We just know the electrode was missing when he pulled that plug...

I think the OP is thinking that a bad coil is causing misfiring and damaging the plug. To that end, I suggested swapping coil packs first before buying a new coil pack.

ok, will do the coil swap tommorow. while i'm at it, will check the new sparkplug in cyl #4. (100 miles so far.)

will also try to remove the sparkplug w/o the rachet. just put in the socket + extender, then turn by hand.... to see if it's loose.

edit:
will not do the coil swap. will buy a Itr6f13 plug and put it into cyl #4. (see below)

 

[JEDI]

The plugs are the incorrect ones for the vehicle. What the op got away with for whatever duration is irrelevant at this point. If OP wants to be a cheap ass, he can purchase a single spark plug that is the correct one, put it in and see if the electrode breaks off... What I think will happen is that OP will find a cylinder misfire in a different cylinder when that spark plug electrode then breaks off because it's the wrong plug for the car. Op will hopefully realize he was wrong and just replace all of the wrong plugs on the car with the correct ones.

dude, the manufacturer put in those sparkplugs since i bought the car new.
and others that have my same year mazda3 have the same itr-5 sparkplugs even tho all the shops say itr-6 version.

ok, will buy a single itr-6 version to put in cyl #4 instead of swapping coil packs.
will check again in 500 miles.

 

[JEDI]

http://forums.anandtech.com/showpost.php?p=32918814&postcount=1

He appears to have already tried a 6 range plug. And swapped out plugs a couple times.

Didn't mention a missing electrode on #4 ITR5F13 when he removed them. Old or new. Or on the 6 range plugs he tried.

no.. tr6ix is not itr6f13.
tr6ix is a compatible sparkplug. it is different than the itr6f13.

advanced auto at that time did not have oem, and the website recommended tr6ix.

advanced auto now has oem

Remember that it's only one cylinder and that cylinder shows carbon buildup in the plug tube. Regardless, it appears that Mazda made a change in the heat range they wanted his engine to use. He should use what's now recommended which is a colder plug.

In researching NGK heat ranges I ran across this which shows how a spark plug dissipates its heat. One can see the importance of having a properly tightened spark plug with full seat contact.

from your link, it says one of the causes for Carbon Fouling is Spark plug heat range too cold.
but the itr-5 is one heat range hotter than the itr-6.

doh.. also from that link is a cause for overheating: Spark plug heat range too hot

damned if i do, damned if i dont?!

"As a general guideline, among identical spark plug types, the difference in tip temperature from one heat range to the next is approximately 70°C to 100°C."

since it seems like cyl #4 is overheating, i will stick with trying the colder itr-6 sparkplug in that cyl.

 

[LTC8K6]

tr6ix is a 6 range plug. Same heat range as itr6f13 and colder than itr5f13.

 

[JEDI]

update:

pulled itr5f13 (200miles). the electrode was still there.
i was able to remvoe it by hand (no rachet).

put in the itr6f13 sparkplug. tightened it a little bit harder w/rachet than what i did w/itr5f13 sparkplug.

drove ~10miles.
heard what i can only describe as soft low level sputtering noises when i let go of the accelerator and am below 20mph.
but my car isnt sputtering. the steering wheel isnt vibrating. i dont hear the noise when i'm pressing on the gas pedal.

the noise is less when i hit the brakes or in park. the idle isnt rough.
i only hear it in the cabin of the car. when i put the car in park and open the hood, i dont hear the sputtering noise.

no check engine lights.

any idea about this noise?

 

[Tsavo]

the steering wheel isnt vibrating more than usual.

Get a new steering wheel.

Problem, solved.

 

[boomerang]

i was able to remvoe it by hand (no rachet).

What is your plan now? I've said that the sparkplug isn't seating and you've now confirmed it.

As far as your new noise I'll bet you left a tool laying under the hood somewhere. Maybe left the old sparkplug laying somewhere.

 

[JEDI]

What is your plan now? I've said that the sparkplug isn't seating and you've now confirmed it.

As far as your new noise I'll bet you left a tool laying under the hood somewhere. Maybe left the old sparkplug laying somewhere.

so if tightening the sparkplug more doesnt help and i've stripped the aluminium threads on the cylinder, then is there an easy fix?

will check for tools under the hood. thx.

also, google says boot might not be on properly and i might be arcing the coil. i dont know how the boot isnt on properly, but i'll re-seat that.