Shrinking Spark Plug Gap

[HadesOmega]

I had smog check due so I did a little tune up before I took it to get tested and I changed the plugs and they looked like this:

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I know plugs are suppose to INCREASE their gap when they get older but these one did the opposite. Cylinders 2 and 3 had this problem. There was almost no gap at all. 1 and 4 were fine. The plugs look great all of them, grey on the tips and look very clean.

Anyone know what could cause this?

My guess is GASP the piston hit the the spark plugs, but I checked the top of the piston through the hole and they looked fine from what I could see. Or maybe these 2 cylinder are getting too hot and the plugs are starting melt. But now that I think about it wouldn't the gap get larger due to gravity?

 

[BLINKY619]

wow never seen that... have you checked the ones that you just installed... and how did the car run with the old spark plugs?

 

[standard235]

I know my cousin's 1g kept smashing plugs shut. No clue why it happened. But now it has no compression on those 2 cylinders. Pulled the pistons and the ringlands fell apart .

But he also had metal shavings on the plugs...

 

[Chicken Patty]

Closing spark plugs can be because of excessive knock I believe.

 

[turboglenn]

Closing spark plugs can be because of excessive knock I believe.

+1 to that, if something was touching there'd be a sign of it on the plug or piston or valve.


My other thought is this...temps reaching high enough in the combustion chamber to soften the small electrode making it prone to "warping" back closed or letting presure from det . close them up a little. I've only heard of detonbation causing this and never seen it first hand so i'm only taking educated guesses here

but since it's only doing this on 2 & 3 i have to wonder if those injectors are getting clogged causing it to run hotter there or if there's some other reason that they are burning different from 1 and 4 which are eusually the most effected by airflow inconsistancy from the manifold.. #1 shuold be the leanest with 4 being the richest, 2&3 being about equal (due to manifold design and airspeed)

But i do know on streetbikes the inner 2 cyinders always get jetted richer (some leaner) than the outter ones and they have an airbox with no directional flow to change volume at the different locations)

 

[HadesOmega]

I haven't checked the new ones yet probably will soon, I'm thinking your right it could be knock also I was driving up a long steep uphill one time on a hot day and the car almost overheated. I'm thinking that may have caused it also. I know at WOT I'm really rich because my friend said he could smell fuel coming out of my exhaust.

The car actually ran good with the plugs like that I didn't notice anything weird until I pulled them.

 

[diambo4life]

That's not definitive if you didn't measure the plugs gaps prior to install. This time, set the plugs at a specific gap and see whether the phenomenon repeats itself.

 

[Chicken Patty]

+1 to that, if something was touching there'd be a sign of it on the plug or piston or valve.


My other thought is this...temps reaching high enough in the combustion chamber to soften the small electrode making it prone to "warping" back closed or letting presure from det . close them up a little. I've only heard of detonbation causing this and never seen it first hand so i'm only taking educated guesses here

but since it's only doing this on 2 & 3 i have to wonder if those injectors are getting clogged causing it to run hotter there or if there's some other reason that they are burning different from 1 and 4 which are eusually the most effected by airflow inconsistancy from the manifold.. #1 shuold be the leanest with 4 being the richest, 2&3 being about equal (due to manifold design and airspeed)

But i do know on streetbikes the inner 2 cyinders always get jetted richer (some leaner) than the outter ones and they have an airbox with no directional flow to change volume at the different locations)

I just changed my spark plugs the other day and I had this happen. Last time I logged my car I had about 7 counts of knock, one pass had 12 but that didn't repeat itself, so could have been anything causing the sensor to pickup some vibrations or something. anyhow, knowing this I avoided stepping on my car as much as possible, but throughout the months you do so a few times. Well, when I pulled out the plugs they had closed up to under .20. Thre was only one that I was able to fit into the gapper which starts at .20 and it was gapped at about .22. Since then I have re tuned the car and this time there's only 1-2 counts top of fourth, none in 3rd so that I feel safe about stepping on my car now.

But anyhow, the issue described in the OP can def. be knock related.