What is destroying sparkplugs in my engine?

[boomerang]

I doubt you've stripped the threads. What exactly happened I can't say but the seat for the plug is no longer concentric with the threads. The seat can be recut with a tool. The tool threads into the plug hole and there is a cutter that will recut the seat. There will be aluminum chips as a result that you really don't want to go into the cylinder which is why way, way, back I suggested you take it somewhere and have it done.

It is also possible to cut the seat too deep and that will allow the end of the spark plug to project too far out of the cylinder head and then you could have an interference problem that could damage the plug. Also, if a thread of the plug is exposed into the combustion chamber it could get hot and cause pre-ignition.

I don't want to bring you down but if the seat is too messed up, it may require more expensive repairs.

Please, don't think I'm talking down to you when I say this. Have this done by a shop with the tools to do it. We all have our limitations and knowing them can save us time and grief in the long run. This is a task you should farm out.

 

[LTC8K6]

The other fellow I posted about with a missing ground electrode also noted that the plug was loose.

 

[LTC8K6]

So we know basically what is happening and why it's only that plug, but we don't know why the plug would come loose. The plug is coming loose and losing it's heat sink, so it's getting too hot.

It's also being hammered back and forth in the threads when the cylinder fires, since it can move a little bit when it's not tight.

Bad threads, bad seat, not tightening that plug enough/using a torque wrench?

Swapped plugs too often with an aluminum head?

 

[boomerang]

So we know basically what is happening and why it's only that plug, but we don't know why the plug would come loose. The plug is coming loose and losing it's heat sink, so it's getting too hot.

IMO, the plug is coming loose because the seat is damaged. Without full contact all the way around the plug, the heat cycles loosen in up.

It's also being hammered back and forth in the threads when the cylinder fires, since it can move a little bit when it's not tight.

Bad threads, bad seat, not tightening that plug enough/using a torque wrench?

Swapped plugs too often with an aluminum head?

I would go back to the beginning. If the factory plug came out with no side electrode, the problem occurred during manufacture. The seat could have been bad initially, or the plug was not sufficiently tightened. Makes little difference at this point because it most certainly is not going to be covered under warranty.

If the problem occurred subsequent to the first plug change there are a number of possibilities. I always loosen spark plugs a turn and then blow around the base of the plug with compressed air. I've been sandblasted a number of times when doing this which confirms to me it's a good practice. Was their dirt under the seat, the plug not tightened properly, bad plug - we may never know.

 

[tortillasoup]

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?

The car has a light misfire because you have too hot of plugs in the other cylinders. Just drive the 500+ miles so you can come back and praise me for being right about the electrode, then we can address this other issue that you've now discovered. I wouldn't keep trying to tighten the spark plug like these people keep suggesting, for aluminum heads, 15ft-lbs is the absolute maximum you should use. Btw when you're installing these spark plugs, IS THE ENGINE STONE COLD? Always install the plugs when the engine is stone cold, not after it has been driven.

 

[boomerang]

The car has a light misfire because you have too hot of plugs in the other cylinders.

Bullshit. Your deductive reasoning skills are minimal at best. People like yourself just confuse people like the OP. I have no problem with people conjecturing to help an individual when it has a basis in reason. Yours has none. Stick to reading articles in Hot Rod.

 

[LTC8K6]

I would go back to the beginning. If the factory plug came out with no side electrode, the problem occurred during manufacture. The seat could have been bad initially, or the plug was not sufficiently tightened. Makes little difference at this point because it most certainly is not going to be covered under warranty.

If the problem occurred subsequent to the first plug change there are a number of possibilities. I always loosen spark plugs a turn and then blow around the base of the plug with compressed air. I've been sandblasted a number of times when doing this which confirms to me it's a good practice. Was their dirt under the seat, the plug not tightened properly, bad plug - we may never know.

IIRC, the factory original ITR5F13 plugs were removed at 80K with no issues according to other posts by the OP.

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

Nothing about a missing electrode or overheated plug.

I suspect his problem began with this plug swapping episode at 80K miles.

And the ITR5F13 plugs are the correct plugs. :biggrin:

 

[tortillasoup]

Bullshit. Your deductive reasoning skills are minimal at best. People like yourself just confuse people like the OP. I have no problem with people conjecturing to help an individual when it has a basis in reason. Yours has none. Stick to reading articles in Hot Rod.

Mazda updated the specification to supersede the -5 plug for a -6 plug likely because of this issue or some other spark plug related issue. Yes the car may have came with a hotter plug but Mazda now specifies the usage of a colder plug, likely for the reason OP is complaining about. The only reason you use a hotter plug is to ensure the plug doesn't get fouled and continues to self clean. Obviously the plug got too hot which is why it broke off.


oh and for reference:
http://www.ngksparkplugs.com/tech_support/spark_plugs/p5.asp?mode=nml

Types of Abnormal Combustion

Pre-ignition

Pre-ignition occurs when the air-fuel mixture is ignited by a hot object / area in the combustion chamber before the timed spark event occurs.
When the spark plug firing end (tip) temperature exceeds 800°C, pre-ignition originating from the overheated insulator ceramic can occur.
Is most often caused by the wrong (too hot) heat range spark plug, and/or over-advanced ignition timing. An improperly installed (insufficient torque) spark plug can also result in pre-ignition due to inadequate heat transfer.
Pre-ignition will dramatically raise the cylinder temperature and pressure and can melt and hole pistons, burn valves, etc.

Knock

Occurs when part of the air-fuel mixture in the combustion chamber away from the spark plug is spontaneously ignited by the pressure from a flame front originating from the spark plug. The two colliding flame fronts contribute to the “knocking” sound.
Knock occurs more frequently when using low octane fuel. Low octane fuel has a low resistance to knock (low resistance to ignition)
Knock is related to ignition timing. (Knock is sometimes referred to as “Spark-knock”.) Retarding the ignition timing will reduce knock.
Heavy knock often leads to pre-ignition.
Heavy knock can cause breakage and/or erosion of combustion chamber components.
Knock is sometimes referred to as “ping” or “detonation”.

Misfires

A misfire occurs when the spark travels the path of least resistance instead of jumping across the gap. Misfires can be caused by the following:

Carbon fouling
Worn or deteriorated ignition system components
Too large of gap size
Spark timing excessively advanced or retarded
Damaged spark plugs (cracked insulator, melted electrodes, etc)
Mismatched ignition system components (plug resistance / wire resistance, ignition coils / igniter modules, etc.)
Insufficient coil primary and/or secondary voltage – voltage required to jump the spark plug gap higher than coil output

 

[LTC8K6]

http://www.protegefaq.net/tsb/mt000004848.html

TSB explains that for 2006, the plugs have changed with a cylinder head redesign.

It also points out that 2004-2005 should use the ITR5F13 plugs.

 

[LTC8K6]

It's apparently just a build date thing. 2004-early 2005 got the 5F13's. Later 2005's got the 6F13's.

Both plugs are apparently in the acceptable heat range for the engine.

 

[LTC8K6]

http://www.protegefaq.net/tsb/01-013-05.html

TSB regarding the ITR5F13 plugs. They were apparently selected by Mazda due to fouling.

 

[boomerang]

Both plugs are apparently in the acceptable heat range for the engine.

Yes, because for everyday driving in a modern automobile with a computer that can very precisely control the air/fuel ratio, it's not all that critical. It was different in the days of carburetors when engine temperatures were much cooler by design. Especially in cars that idled a lot (police cars, taxis) and it would be very critical in a car engineered to run at the Bonneville Salt Flats which would run at WOT for miles.

I'm anxious to hear how the OP made out.

 

[JEDI]

Yes, because for everyday driving in a modern automobile with a computer that can very precisely control the air/fuel ratio, it's not all that critical. It was different in the days of carburetors when engine temperatures were much cooler by design. Especially in cars that idled a lot (police cars, taxis) and it would be very critical in a car engineered to run at the Bonneville Salt Flats which would run at WOT for miles.

I'm anxious to hear how the OP made out.

didnt see any tools.
re-seated boot.
still hear that noise at under 20mph when no accelerator (coasting to a stop) and when stopped.

drove 50miles round trip hwy yesterday @70mph. gas 34mpg.

ironically, when i had the itr5f13 in cyl #4, i got 36mpg for that same trip.


edit:
hm.. since the noise only occurs when i let go of the gas pedal, then i can rule out detonations?

 

[tortillasoup]

didnt see any tools.
re-seated boot.
still hear that noise at under 20mph when no accelerator (coasting to a stop) and when stopped.

drove 50miles round trip hwy yesterday @70mph. gas 34mpg.

ironically, when i had the itr5f13 in cyl #4, i got 36mpg for that same trip.


edit:
hm.. since the noise only occurs when i let go of the gas pedal, then i can rule out detonations?

Well the question becomes, is the car in DFCO (Deceleration Fuel Cut Off) when you're letting go of the accelerator? I don't know what the cut off is for your car but the general rule is 2000+ RPM (some cars have lower threshold) with no throttle and zero load = DFCO. If you could "engine brake" above 2K RPM with no throttle (hence engine braking for sure) that would clarify things a bit. I can't imagine how a car would have detonation while in DFCO since there is no fuel to combust. Try again to confirm you're in DFCO, maybe down a kinda steep hill or getting off the highway in like 2nd or 3rd gear or something that allows you to engage DFCO quite readily. Maybe driving the car up to 3-4K then releasing the throttle, that should definitely engage DFCO. But yeah if you're in DFCO and it's making a funny sound, that isn't detonation. (Unless someone else could explain otherwise, I'm all ears, lol.)