Why does a sparkplug work in my car w/the tip missing?!

[monkeydelmagico]

The plugs are TOO hot, you were suppose to go to colder plugs but you obviously didn't which is why your electrodes broke off... as for why the engine can still run with no electrode, it's because w/o an electrode you basically increase the gap to the edge of the spark plug where the electrode connects to.

Is the OP melting them or is the cylinder hitting the bottoms? I've heard of smashed plugs when thread depth is off. Never actually seen it myself, but then again I've never seen a spark plug work without an electrode either.

 

[JEDI]

I can see you learned absolutely NOTHING from that thread. beyond help...

The plugs are TOO hot, you were suppose to go to colder plugs but you obviously didn't which is why your electrodes broke off... as for why the engine can still run with no electrode, it's because w/o an electrode you basically increase the gap to the edge of the spark plug where the electrode connects to.

lol.. car came with Ngk ITR5F spark plugs.
I also used Ngk ITR6F.

cyl #4 also ate the ground plug off the ITR6F's too

 

[tortillasoup]

lol.. car came with Ngk ITR5F spark plugs.
I also used Ngk ITR6F.

cyl #4 also ate the ground plug off the ITR6F's too

If you followed Mazda's suggestion which is to use the ITR6F and the electrode keeps breaking off, it's possible that you need an even colder plug for that specific cylinder. But considering you lost an electrode on two cylinders instead of just one, it was more likely due to too hot of a plug. Since you do a lot of highway driving and whatnot, I wouldn't concern myself with the electrode being too cold.

 

[pcgeek11]

hm.. maybe you are right that cyl #4 isn't sparking.

the tops of cyl #1,2,&3 are all coated w/carbon.
Cyl #4 is clean.

so is this why I have so much carbon buildup?
engine is pumping enuf fuel for 4 spark plugs but only 3 are sparking thus they are burning rich?

Cylinder # 4 is clean because it is not sparking nor burning any fuel. That is also why it is so clean, the gasoline is washing it off.

That unburned fuel from #4 will also damage your cat(s), iirc.

It will also cause the cylinder rings to wear due to washing the oil from the cylinder walls.

 

[tortillasoup]

Cylinder # 4 is clean because it is not sparking nor burning any fuel. That is also why it is so clean, the gasoline is washing it off.



It will also cause the cylinder rings to wear due to washing the oil from the cylinder walls.

funny but likely correct. It would explain why OP didn't have a check engine code when he had his broken plug in there but did have a check engine code when he put a new plug in there. The car actually began to fire on that 4th cylinder with the new plug in it so he reverted to the bad plug so the check engine code would go away...

I just can't believe OP could drive a car so long on 3 cylinders and not notice a problem --check engine code or not.

 

[rommelrommel]

I also wonder how he's calculating the 34 mpg or whatever he's claiming.

 

[Ferzerp]

I just can't believe OP could drive a car so long on 3 cylinders and not notice a problem --check engine code or not.

Have you seen the rest of his threads about his car? I can certainly believe it

 

[PlasmaBomb]

Oh god... this is still going.

So how does a sparkplug run w/o a tip??

You have already answered your own question - badly

I noticed I'm not accelerating as quickly anymore

 

[JEDI]

I also wonder how he's calculating the 34 mpg or whatever he's claiming.

# gallons at fillup at gas station.
# of miles on tripometer.

simple division. save information.
reset tripometer.

for the past 6months I avg 32mpg.
i'll look for the rest of my notes to calc the mpg for the history of my car.

 

[JEDI]

PlasmaBomb,
"I noticed I'm not accelerating as quickly anymore "

that's with 2 sparkplugs w/o the ground prong.

altho I suppose I got used to 3 working sparkplugs and forgot how the car accelerates with all 4 working.

 

[JEDI]

It would explain why OP didn't have a check engine code when he had his broken plug in there but did have a check engine code when he put a new plug in there. The car actually began to fire on that 4th cylinder with the new plug in it so he reverted to the bad plug so the check engine code would go away...

ahhh.. makes sense.

but if you have a car w/all the sparkplugs working, put it in park and unplug one of the sparkplugs, the car would shake and sound awful.

mine doesn't do that. with 3 sparkplugs working, my car doesn't make any more noises than the car next to me when stopped at a red light

 

[exar333]

Just the tip? Lol

 

[C1]

I see that the Mazda has separate ignition coils for each plug.

The whole system needs to be put on a SUN machine for analysis & diagnosed across the board, but particularly the electrical system (as you could easily have one or more bad ignition coils).

 

[rommelrommel]

The whole car needs to be sold for scrap.

ftfy

 

[tortillasoup]

ahhh.. makes sense.

but if you have a car w/all the sparkplugs working, put it in park and unplug one of the sparkplugs, the car would shake and sound awful.

mine doesn't do that. with 3 sparkplugs working, my car doesn't make any more noises than the car next to me when stopped at a red light

Depending on which plug isn't working, you can make a car idle fairly smoothly or idle really poorly just by having a "misfire" or a non firing plug on a certain cylinder.

https://www.youtube.com/watch?v=QSNjtNYuD18

This guy has 4 episodes and in the episodes I believe he talks about how he specifically chose a certain cylinder to disable as some worked better than others.

 

[JEDI]

Depending on which plug isn't working, you can make a car idle fairly smoothly or idle really poorly just by having a "misfire" or a non firing plug on a certain cylinder.

http://www.amazon.com/gp/offer-listi...&startIndex=40

This guy has 4 episodes and in the episodes I believe he talks about how he specifically chose a certain cylinder to disable as some worked better than others.

um.. your link is to a fitbit exercise thingy?!

 

[Brian Stirling]

It would be interesting to see what a borescope would reveal in the cylinders.


Brian

 

[tortillasoup]

fixed the url

 

[JEDI]

fixed the url

thx. :thumbsup:

1) hm.. so my cyl #4 probably isn't sparking since the spark plug does have a ground prong.
but fuel is still going into the cylinder. this makes the car run rich, thus all the carbon?
shouldn't the computer notice that I'm running rich and compensate?

2) in the video, he unplugged both the sparkplug and the fuel injector so no more fuel into the that cylinder.
but the car ran rough!

what if I unplugged the fuel injector but left the sparkplug in?

 

[tortillasoup]

The car can't compensate well because there is only one o2 sensor before the catalytic converter but after the 4 - 1 header combination. Now if there was an o2 sensor per cylinder, then yes it could compensate correctly. Right now though, if you have an injector that doesn't fire or is lean/rich, all the other cylinders will be forced to increase or decrease their output, even if it isn't optimal.

Car engines are designed with the presumption that all injectors fire the same amount of fuel, all spark plugs fire with the same intensity, all cylinders have the same compression ratio, etc. etc. Yes they COULD make it significantly more precise by having an o2 sensor after each cylinder but I've yet to see an automaker do that.