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

[JEDI]

(2005 Mazda3i AT)

from this 2011 thread that someone necro'd:
http://forums.anandtech.com/showthread.php?t=2183587

at the time of that thread my car was a 125k miles.
I have no idea how long I've been driving w/a tipless sparkplug in cylinder #4.

every other sparkplug (oem and others) that I put in there ate the tip and gave me a misfire code.
the original sparkplug did not give me a code, so I put it back in.

fast forward to 2014 and 75k miles later.
at 200k miles, I'm now driving around with TWO tipless sparkplugs. (Cylinder #4 and #3)

I think around 5k miles ago is when cyl #3 ate the tip because that's when I noticed I'm not accelerating as quickly anymore.

I confirmed that today. while I was doing work to clean the throttle body, I decided to check the spark plugs (thanks to the necro'd thread) to see if any others lost a tip.
yup cyl #3.
Cyl #2 is fine. I didn't bother to check cyl #1.

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

 

[Nebor]

Uh... more importantly, where are the tips?

 

[JEDI]

Uh... more importantly, where are the tips?

when I went to clean the throttle body, I saw a sliver of metal that looks like a ground prong.
it was sitting on a coating of carbon.

I couldn't reach it with my fingers.

 

[PottedMeat]

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

all it needs is enough voltage to bridge the gap, wider -> higher voltage

...at least you know where one is - i wouldn't want any bits of metal floating around the intake. weird that it got blown out the intake though.


maybe the other one is tearin' shit up in the cylinder? or it got stuck in the cat or muffler?

 

[pcgeek11]

(2005 Mazda3i AT)



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

It doesn't spark without a ground tip. That is why your car runs like shit.

 

[rommelrommel]

Here is post number 32947802957 in the series entitled "I think it's time to go to a mechanic."

 

[JEDI]

It doesn't spark without a ground tip. That is why your car runs like shit.

it ran fine for the past 75k miles.
idled smooth at 750 rpm. 32mpg at 70% hwy. (car is rated 34mpg pure hwy)

but I heard a car runs awful if you remove the sparkplug while the car is on.

so if my sparkplug w/o the ground prong isn't sparking, why isn't my car acting like it's missing a sparkplug??

 

[rommelrommel]

At best it's arcing out to the cylinder wall or piston and burning the gas to some extent, at worse you just aren't noticing the miss.

 

[comphollic]

it ran fine for the past 75k miles.
idled smooth at 750 rpm. 32mpg at 70% hwy. (car is rated 34mpg pure hwy)

but I heard a car runs awful if you remove the sparkplug while the car is on.

so if my sparkplug w/o the ground prong isn't sparking, why isn't my car acting like it's missing a sparkplug??

The computer most likely is adjusting the voltage for that plug and probably causing the carbon build up. Eventually the plug was going to completely fail and then you would notice the loss of performance. Run seafoam to clean your engine like

http://seafoamsales.com/vacuum-line-method-with-sea-foam/

Then change all spark plugs and cables. And remember to change spark plugs every 50k miles. I would not waste money on those rated for 100k. If you can get oem or similar, changing spark plugs is easy and quick to do.

 

[JEDI]

It doesn't spark without a ground tip. That is why your car runs like shit.

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?

 

[LTC8K6]

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

 

[LTC8K6]

the original sparkplug did not give me a code, so I put it back in.

fast forward to 2014 and 75k miles later.

Does that mean you left that plug in for 200K?

 

[silicon]

put some new correct sparkplugs now into your vehicle. when you were examining them they should have been tossed for new ones. get some high quality platinum plugs that will last a long time.

 

[JEDI]

Does that mean you left that plug in for 200K?

i think so

 

[Pacfanweb]

It works because today's ignition systems are badasses and can jump a HUGE gap, so the plug is probably still firing and just arcing to the bottom of the threads.

And there's no way in hell you see a piece of the spark plug in the throttle body.

 

[JEDI]

It works because today's ignition systems are badasses and can jump a HUGE gap, so the plug is probably still firing and just arcing to the bottom of the threads.

And there's no way in hell you see a piece of the spark plug in the throttle body.

i'll take a look again.
car still sputters slightly when stopped a red light.
will probably take the throttle body off to clean it.

and at the same time, reach in there and scoop out the carbon in the engine as well see what that small metallic looking object is

 

[comphollic]

Did you change the spark plugs and wires? I would strongly suggest you doing that since it seems they were never changed lol.

 

[JEDI]

Did you change the spark plugs and wires? I would strongly suggest you doing that since it seems they were never changed lol.

changed 3 of the 4 spark plugs like 60k miles ago. (100k iridiums)
sparkplug in cyl #4 has been there for the whole 200k miles.

that's the only spark plug that wouldn't give me a check engine light.

I replaced it w/an oem sparkplug. it ate the ground prong and gave me a misfile cyl #4 cel.
and it ate the ground prong of 2 other brands and gave me a misfire cel.

so i left the one that came w/the car when I bought it new, missing ground prong and all.

 

[comphollic]

The iridium may be rated for 100k but that's under normal conditions and from the looks of it, your engine is far from running normal. I would replace all the sparkplugs with platinum ones, not iridium and new wire set... I don't think I've seen anyone recommend not changing all of them at the same time...
Sea foam your car first then change the plugs.

Honestly I'm surprised your car hasn't given you more problems lol...

 

[Carson Dyle]

Wait a minute... You actually took that picture of a dead spark plug and then you PUT IT BACK??

You shouldn't be seeking mechanical advice. You should be asking about the easiest way to push your car off a cliff.

 

[JEDI]

Wait a minute... You actually took that picture of a dead spark plug and then you PUT IT BACK??

You shouldn't be seeking mechanical advice. You should be asking about the easiest way to push your car off a cliff.

200k miles so far on that sparkplug w/o a ground prong

 

[Kadarin]

Just the tip?

 

[cabri]

Why would you not change all the plugs at the same time?

 

[tortillasoup]

(2005 Mazda3i AT)

from this 2011 thread that someone necro'd:
http://forums.anandtech.com/showthread.php?t=2183587

at the time of that thread my car was a 125k miles.
I have no idea how long I've been driving w/a tipless sparkplug in cylinder #4.

every other sparkplug (oem and others) that I put in there ate the tip and gave me a misfire code.
the original sparkplug did not give me a code, so I put it back in.

fast forward to 2014 and 75k miles later.
at 200k miles, I'm now driving around with TWO tipless sparkplugs. (Cylinder #4 and #3)

I think around 5k miles ago is when cyl #3 ate the tip because that's when I noticed I'm not accelerating as quickly anymore.

I confirmed that today. while I was doing work to clean the throttle body, I decided to check the spark plugs (thanks to the necro'd thread) to see if any others lost a tip.
yup cyl #3.
Cyl #2 is fine. I didn't bother to check cyl #1.

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

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

http://forums.anandtech.com/showthread.php?t=2335923
http://forums.anandtech.com/showthread.php?t=2336069
http://forums.anandtech.com/showthread.php?t=2333372



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.

 

[schmuckley]

Uh... more importantly, where are the tips?

^This