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#4655885 - 02/04/18 12:38 PM What goes wrong with Spark Plugs?
NibbanaBanana Offline


Registered: 05/23/16
Posts: 292
Loc: New England
I have changed many, many spark plugs in my life but don't ever recall having a bad spark plug. I changed the spark plugs on the wife's Kia yesterday. The old Champion copper plugs were essentially perfect. The gap had opened about .005 in 30K miles but if I had regapped them I don't see why they wouldn't have gone another 30K no problem.

Have I just been tossing perfectly fine spark plugs all these years? What goes wrong with these things? It would be interesting to see how many miles could be gotten out of a set of spark plugs. Remove, inspect, regap, reinstall.
_________________________
1993 Ford E350 5.8L, 68K
2002 Ford E150 4.2L, 85K
2006 Chevy Aveo 1.6L 215K
2013 Kia Reo 1.4L, 101K
7500 OCI, M1 5-30 winter, M1 10-30 summer

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#4655888 - 02/04/18 12:44 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
KzMitch Offline


Registered: 01/02/15
Posts: 374
Loc: Chicago Burbs
Rooting for the asteroid!

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#4655893 - 02/04/18 12:46 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
CT8 Offline


Registered: 10/09/14
Posts: 10946
Loc: Idaho
They wear out or leak current or have defects from the factory and then some.
_________________________
"Don't let your preconceived notions get in the way of facts."
Geoff Metcalf

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#4655904 - 02/04/18 12:55 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
92saturnsl2 Offline


Registered: 03/02/04
Posts: 1268
Loc: Flaherty, KY
I see two "normal" failure modes:

1) the gap opens up too large, which requires too high ignition voltage to fire
2) wear on the electrodes (center or outside) creates a rounded surface, which with increasing gap, this can requirer very high voltage to fire that the ignition system can't handle

I've only observed two outright spark plug failures:

One was on a vehicle I owned (2001 Frontier supercharged), the ceramic insulator surrounding the center tip broke apart. The truck would have an intermittent misfire and when I pulled the plugs, that is what I found on one plug. I have no idea what happened to the ceramic, it probably got crushed by the pistons and spit out the exhaust. Changed plugs and engine worked fine with no more misfire.

The other was a good friend of mine that does absolutely zero maintenance to his vehicles other than random oil changes. He fixes things when they break, which hasn't been too terribly a bad approach for him, as his vehicles routinely go 200k+ miles. Sure increases your chance of a breakdown on the side of the road though. He brought his 2008 Jeep Commander (hemi with 16 plugs IIRC) to me w/ 100k miles on it, said the engine was misfiring. We pulled the plugs and the originals were copper plugs with a lifespan of typically 36k miles. The center electrode was basically non-existant-- it was sunken down so far into the ceramic insulator, you could hardly see it. You could see arc trace marks across the ceramic insulator where it had been firing. The side conductor looked like the tip of a nail-- it has worn mostly away.

Spark plugs will never be something that will give you horsepower-- but they can hobble an engine if you let them go WAY too long, or there's some mechanical failure with them like a broken insulator.

_________________________
1985 F-250HD 7.5L 4x4 135k- Maxlife 15w-40 HDEO [for sale]
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#4655905 - 02/04/18 12:56 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
demarpaint Offline


Registered: 07/03/05
Posts: 29751
Loc: NY
Google "spark plug wear chart", you'll see a ton of pics of normal wear, and everything in between.
_________________________
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#4655915 - 02/04/18 01:02 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
supton Online   content


Registered: 11/09/08
Posts: 11924
Loc: NH
I have to wonder if they are using a plating of some sort. Which, once worn through, would rapidly wear away.

Not sure how many misfires it takes to damage a cat. For the time and effort it takes to inspect... you can just replace. I guess you could keep spark plugs on the shelf in case you find a bad one--but then you've spent the money, and then you've spent the time, so why not just stuff in new ones & motor on for another 100-120k? [Assuming that is the replacement interval.]
_________________________
2011 Toyota Camry, base, 2.5L/6MT, 160k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 143k, ours
1999 Toyota Camry LE, 2.2L/4AT, 181k, his

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#4655928 - 02/04/18 01:11 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
Trav Offline


Registered: 11/20/06
Posts: 18856
Loc: MA, Mittelfranken.de
Other than electrode erosion, mechanical damage and fouling the only plug I have had a hard internal fail on was a new AC Delco back in the mid 70's. Probably shorted to ground inside for some reason, it failed within a few miles, otherwise there was always an obvious reason for the failure.
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#4655929 - 02/04/18 01:14 PM Re: What goes wrong with Spark Plugs? [Re: supton]
Wolf359 Offline


Registered: 04/27/12
Posts: 4746
Loc: MA
Originally Posted By: supton
I have to wonder if they are using a plating of some sort. Which, once worn through, would rapidly wear away.

Not sure how many misfires it takes to damage a cat. For the time and effort it takes to inspect... you can just replace. I guess you could keep spark plugs on the shelf in case you find a bad one--but then you've spent the money, and then you've spent the time, so why not just stuff in new ones & motor on for another 100-120k? [Assuming that is the replacement interval.]


Yeah, there are certain things you can re-use, but we're not in Cuba, if you're going to take the spark plugs out, just put new ones in. I think one of the failures is that the ceramic insulator cracks and falls off bouncing around in your engine.

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#4655996 - 02/04/18 02:23 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
blupupher Offline


Registered: 08/27/04
Posts: 4421
Loc: Katy, Republic of Texas
The electrodes wear out:



150,000 miles on an '04 F150

And these are off my sisters '10 Santa Fe with 150,000 miles:



Still looked good, gap was alittle larger than stock, but was running rough and hard to start.

I pulled the plugs off my mom's Saturn Vue with 120,000 miles and they looked new, but replaced them anyway.

Platinum/iridium has greatly improved spark plugs, especially the double tipped and fine wire ones.
_________________________
1994 Honda VT1100C: Peak 15w-40/TG/2500 mile OCI
2002 Ford F150: GTX HM 5w-20/EcoGard Syn/1yr OCI
2012 Scion xB: QSUD 0w-20/CQ Blue/5k OCI


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#4656000 - 02/04/18 02:29 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
Reddy45 Offline


Registered: 08/15/08
Posts: 2967
Loc: USA
Blupupher are those the infamous F150 plugs that end up requiring helicoil work to remove?

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#4656011 - 02/04/18 02:38 PM Re: What goes wrong with Spark Plugs? [Re: Reddy45]
blupupher Offline


Registered: 08/27/04
Posts: 4421
Loc: Katy, Republic of Texas
Originally Posted By: Reddy45
Blupupher are those the infamous F150 plugs that end up requiring helicoil work to remove?

No, these were the ones from the 3v 5.4 that broke in half when removing (I luckily got all 8 out unbroken).
The 2v 5.4 is the one that would spit out plugs and require a repair.
_________________________
1994 Honda VT1100C: Peak 15w-40/TG/2500 mile OCI
2002 Ford F150: GTX HM 5w-20/EcoGard Syn/1yr OCI
2012 Scion xB: QSUD 0w-20/CQ Blue/5k OCI


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#4656090 - 02/04/18 03:55 PM Re: What goes wrong with Spark Plugs? [Re: Wolf359]
NibbanaBanana Offline


Registered: 05/23/16
Posts: 292
Loc: New England
Originally Posted By: Wolf359
Originally Posted By: supton
I have to wonder if they are using a plating of some sort. Which, once worn through, would rapidly wear away.

Not sure how many misfires it takes to damage a cat. For the time and effort it takes to inspect... you can just replace. I guess you could keep spark plugs on the shelf in case you find a bad one--but then you've spent the money, and then you've spent the time, so why not just stuff in new ones & motor on for another 100-120k? [Assuming that is the replacement interval.]


Yeah, there are certain things you can re-use, but we're not in Cuba, if you're going to take the spark plugs out, just put new ones in. I think one of the failures is that the ceramic insulator cracks and falls off bouncing around in your engine.


I agree entirely. It's very cheap insurance if there's a reason.
_________________________
1993 Ford E350 5.8L, 68K
2002 Ford E150 4.2L, 85K
2006 Chevy Aveo 1.6L 215K
2013 Kia Reo 1.4L, 101K
7500 OCI, M1 5-30 winter, M1 10-30 summer

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#4656180 - 02/04/18 05:57 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
Rick in PA Offline


Registered: 01/04/03
Posts: 3203
Loc: Southeastern, PA
Off the top of my head, I can only recall a few spark plug failures:

My car had a slight stumble, so I changed the plugs. These were double platinums, same brand I had run before. I usually change them out at 50k miles (cheap insurance). At ~25k miles, two of the four plugs had worn the platinum electrode totally away. New plugs fixed the stumble. Probably a manufacturing defect, either poor weld of platinum to electrode or bad platinum alloy.

My wife's van was throwing a code for a misfire in cylinder one. I had a shop diagnose it, cracked spark plug insulator. Probably installation failure on my part. Number one cylinder was difficult to get to and I had recently changed the plugs.

Many years ago, my wife's car wouldn't start. I believe this was our first car with fuel injectors. My brother had a shop at the time and he fixed it. Fouled spark plugs due to fouled fuel injectors. He advised me to run a can of fuel injector cleaner through the car once a year. I've been doing that since and never encountered the problem again (today's fuels and injectors are probably improved, but it's cheap insurance).
_________________________
A wise man told me:
"Heat is your friend." and "Any oil is better than no oil."

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#4656195 - 02/04/18 06:22 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
CR94 Offline


Registered: 03/20/16
Posts: 1120
Loc: Western S.C. since 1996
Originally Posted By: NibbanaBanana
... The old Champion copper plugs were essentially perfect. ... Have I just been tossing perfectly fine spark plugs all these years? What goes wrong with these things? It would be interesting to see how many miles could be gotten out of a set of spark plugs. Remove, inspect, regap, reinstall.
Using that strategy, I ran old Champion copper plugs well over 100K a couple of times in the Mazda below. It didn't run noticeably better when they were replaced. The NGKs that were the first two sets in that car likely could've done the same, but I replaced them prematurely, following Mazda's recommended interval of 30K.
_________________________
2011 Toyota Prius now at 88K
1981 Mazda GLC (323) retired at 606K
1972 Subaru DL retired at 190K
1954 Chevrolet retired at 121K

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#4656198 - 02/04/18 06:24 PM Re: What goes wrong with Spark Plugs? [Re: NibbanaBanana]
slacktide_bitog Offline


Registered: 03/20/08
Posts: 6145
Loc: USA
sometimes oil leaks from the valve cover gasket and/or spark plug tube seal, fouling the plugs in no time hide

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