What is destroying sparkplugs in my engine?

[JEDI]

2005 mazda3i AT, 175k miles

i replaced my sparkplugs myself last month with the same OEM iridiums that was in my car when i bought it new.

i'm on my 2nd gas tank (~500 miles).
after a stop, i accelerated like normal and the check engine light flashed a couple of times, then stayed on.

odb II scanner says PO304: Cylinder #4 Misfire.

i took the sparkplug out and it's missing the tip! this is the 3rd time! WTF?!

New sparkplug (500 miles):

Close up pic: http://i.imgur.com/7qBOnPz.jpg

this happened 2yrs ago at 125k miles:
http://forums.anandtech.com/showthread.php?t=2183587

when i replaced the sparkplugs at 174k miles, the tip on sparkplug #4 was also missing.
but car wasnt giving me a check engine light?!
so i've been driving around with just 3 sparkplugs for 50k miles?! (and was still getting 33mpg hwy)

1) so what is eating the tips of the sparkplugs?! could it be the coil pack?

2) what happens if i dont even put a sparkplug in cylinder #4? will the car still drive?
if not, then how am i driving normally with only 3 functioning sparkplugs?

 

[Moonrise]

Could be poor sparkplug gaps causing some detonation and damage to the plugs or bad fuel fouling them. Hard to really say, but removing the sparkplug will be bad news. Believe me, you will notice a significant difference because you will flood the shit out of that cylinder and get no firing at all. Right now it seems you are still somehow getting spark which is why you didn't notice the issue before. You also could have had it just happen so you may not have driven much with the damaged plug.

anyways, don't leave the plug out. You will not get compression or spark in the cylinder and it will just be bad news all around.

 

[JEDI]

Could be poor sparkplug gaps causing some detonation and damage to the plugs or bad fuel fouling them. Hard to really say, but removing the sparkplug will be bad news. Believe me, you will notice a significant difference because you will flood the shit out of that cylinder and get no firing at all. Right now it seems you are still somehow getting spark which is why you didn't notice the issue before. You also could have had it just happen so you may not have driven much with the damaged plug.

anyways, don't leave the plug out. You will not get compression or spark in the cylinder and it will just be bad news all around.

thx for the info about leaving the sparkplug out all together. guess having one w/o tip is better than none at all.

as for plug gaps/bad fuel:
this is the THIRD sparkplug in that same cylinder (#4) that lost it's tip in 50k miles.

all the gaps are factory.

any ideas on what is causing that cylinder to keep eating the tips?

 

[Moonrise]

There are quite a few things. There could be bits damaging the piston, which would cause hot spots on the surface (and again, detonation after a while) that could chew up your spark plug tips. Alternatively, they could be bad plugs, but in general NGK is very good so that is a bit of a stretch, especially if it keeps happening in the same cylinder. That said, Iridium plugs do have a tendency to break more because they have smaller electrodes I believe. Honestly, it is a very real possibility but it seems strange that it keeps happening in only that 4th cylinder.

Another possibility is a bit less fuel being dispensed into the cylinder (low flowing fuel injector), which would again cause a lean mix and detonation in that cylinder.

 

[Meghan54]

You sure you've got the right plugs? I looked on Rock Auto and a couple of other places and every one lists your plug with a part number that is exactly like yours except has a 6 in place of the 5. Just wonder if you have the right heat range of plugs in there.

As to why it continues to work despite having no ground electrode....the spark is being made by using some other local piece of metal as the ground, like the head. It'd be a longer spark, and weaker, so more likely to blow out from compression, giving misfire. But at least it'd fire most of the time.

Gotta say, if there's no damage to that #4 cylinder, you've got to be one of the luckiest SOB's I've ever seen.

 

[JEDI]

You sure you've got the right plugs? I looked on Rock Auto and a couple of other places and every one lists your plug with a part number that is exactly like yours except has a 6 in place of the 5. Just wonder if you have the right heat range of plugs in there.

As to why it continues to work despite having no ground electrode....the spark is being made by using some other local piece of metal as the ground, like the head. It'd be a longer spark, and weaker, so more likely to blow out from compression, giving misfire. But at least it'd fire most of the time.

Gotta say, if there's no damage to that #4 cylinder, you've got to be one of the luckiest SOB's I've ever seen.

yes, have the correct spark plug. ITR5F were the original ones i pulled from the engine and i bought the car new.
and yes, every shop says ITR6F is the correct plug. dont know why.

i dont see any dmg to cyl #4. just black soot.

so how do i stop cyl #4 from destroying spark plug tips? would replacing the coil pack help?

 

[Fenixgoon]

my first thought would be incorrect gap, but if that were the case, you would think ALL the cylinders would have plugs going bad.

 

[Ferzerp]

My non-mechanic mind goes to detonation. Is that cylinder fueling properly (else it may be too lean and detonating)? Do you ever hear knocking or pinging noises? Also, if they're actually breaking off in there, I'm not sure how you don't have damage to the cylinder.

 

[C1]

An engine with that many miles and producing that kind of problem needs thorough inspection and testing. The sensors, fuel injectors, cylinder compression, emission levels, etc. should be checked/gauged.

There is a possibility of bad fuel injector or air leak resulting in hot spot/cylinder over temp (note the almost too clean porcelain insulator). (If there is one bad injector, can the others be far behind?)

Addendum

Carbon build up within a cylinder has been know to result in misfire and/or detonation.

 

[JEDI]

My non-mechanic mind goes to detonation. Is that cylinder fueling properly (else it may be too lean and detonating)? Do you ever hear knocking or pinging noises? Also, if they're actually breaking off in there, I'm not sure how you don't have damage to the cylinder.

no knocking or pinging noises.

i'm assuming the metal piece went out thru the exhaust?

An engine with that many miles and producing that kind of problem needs thorough inspection and testing. The sensors, fuel injectors, cylinder compression, emission levels, etc. should be checked/gauged.

There is a possibility of bad fuel injector or air leak resulting in hot spot/cylinder over temp (note the almost too clean porcelain insulator). (If there is one bad injector, can the others be far behind?)

Addendum

Carbon build up within a cylinder has been know to result in misfire and/or detonation.

how do i clean the carbon build up? just stick a wet paper towel down the cylinder then stick a dry paper towel?

 

[Pacfanweb]

Best way to clean carbon is with water.

Water in a bottle. Remove a SMALL vacuum hose.

Have someone rev engine up a little bit.

Stick hose in water, then remove. You'll hear the engine RPM lower when the water gets there, so you don't want to just leave the hose in the water.

Keep doing that. Run a bottle of water through it. It'll clean carbon better than any chemical you can buy.

 

[JEDI]

huh? how do i get the water into the cylinder while the engine is running?

 

[imagoon]

ITR5F-13 ITR6F-13 are the same except the ITR6F-13 is a colder plug. Either should work but the ITR6F-13 would be better for modified or harder driven engines. You may want to scope the engine and see if the piston is hitting the plug.

 

[imagoon]

huh? how do i get the water into the cylinder while the engine is running?

Through a vacuum line like he mentioned in the post.

 

[JEDI]

Through a vacuum line like he mentioned in the post.

um.. what/where is a vacuum line in the car?

and how less effective is it to just wipe it down w/a damp towel?

 

[imagoon]

http://lmgtfy.com/?q=vacuum+line+2005+mazda+3

I see several that would work. The brake cylinder lines normally work pretty well.

Steam cleaning via water will do more than just wiping it off.

 

[Mark R]

huh? how do i get the water into the cylinder while the engine is running?

Video of how to do it

Recommend that you use distilled water, to avoid lime scale and other stuff building up in the cylinder.

Use a brick or something on the accelerator pedal to keep the revs at about 3000. Don't do it during idle, the engine will run like crap, and the water won't all go into the cylinders, it'll pool in the manifold, and when you rev the engine up, it'll get gulped into the cylinders and you will have a very unhappy engine (I learned this from experience).

 

[Bartman39]

Close up pic: http://i.imgur.com/7qBOnPz.jpg

Take note of how white the insulator is...? What does this mean...? To me it appears he has an injector not putting the proper fuel to that cylinder or it would be a nice tan color... Also if it were not firing correctly it would be black in color due to excess fuel not being burnt... All this being said I would say detonation is the cause for the loss of the ground prong... I would be looking more in the direction of fuel delivery as the issue...

 

[Greenman]

I don't see how you could have the tips off of three or four spark plugs run through that cylinder without some damage. I'd stick a scope in the spark plug hole and have a look see.

 

[twinrider1]

Swap #4 injector with another cylinder. See if problem follows the injector.

 

[Ferzerp]

Swap #4 injector with another cylinder. See if problem follows the injector.

When it is likely causing cylinder damage that he hasn't found yet? Is that a risk you'd take?

 

[twinrider1]

It's happened 3 times in 50k miles. Not feeling a sense of urgency or risk of damage.

 

[JEDI]

here's a pic of the carbon buildup in cylinder #4 before i removed the sparkplug:

close up pic: http://i.imgur.com/zqksJlv.jpg

question:
How does carbon buildup ABOVE the sparkplug nut cause detenation?
i have since cleaned out the soot with a damp paper towel and put in a new oem iridium spark plug.

Hopefully this fixes the problem?
next will be changing out the coil pack??

 

[Tsavo]

here's a pic of the carbon buildup in cylinder #4 before i removed the sparkplug:

close up pic: http://i.imgur.com/zqksJlv.jpg

question:
How does carbon buildup ABOVE the sparkplug nut cause detenation?
i have since cleaned out the soot with a damp paper towel and put in a new oem iridium spark plug.

Hopefully this fixes the problem?
next will be changing out the coil pack.

They are talking about carbon in the cylinder, not on the outside. Also, don't do any water treatments or anything else. The valves will smack into the plug long before the piston will.

I'd try using the EXACT specified spark plug with the proper heat range, and not something "compatible".

 

[Ferzerp]

It's happened 3 times in 50k miles. Not feeling a sense of urgency or risk of damage.

Most recently in under 500 miles.....