I did a compression test because I've had a ticking coming from my engine for a while now... Turns out my compression is just fine, with all cylinders between 230-240 psi, but there was a problem with the spark plug in the No.4 cylinder.

The gap was at about .02 and there was a bit of build up (deposits) on the spark plug. I decided to re-gap the plug and file down some of the deposits for the time being and now the ticking has gone down considerably.

Now my question is, what could cause the gap to go so far out of spec? Does this just happen over time?

 

I don't think modern day fuel injected cars with modern day spark plugs just do this over time. We have examples of very high mileage S2000 that have not exhibited this sort of thing. I think, in your case, you may have some other issue going on that has caused the gap to be what it is and to have the deposits that you speak of. While deposits can happen due to something not working right (spark plug itself, injectors, etc.), gaps just don't close like this. It had to have been that narrow to begin with. Who put them in last?

 

I had my whole cylinder head replaced under warranty due to a cracked cam tower so, though I'm not positive, they might have replaced the spark plugs then. It was all done by Rock Honda here in Fontana, California.

So, do you figure the dealership might have just screwed this up?

 

I'll check back here in a few hours... I have a to go take a final.

Thanks for any info you guys can give me.

 

Putting on a new head would require either using the old plugs or putting in new ones. So many people (including techs) have this misconception that plugs come pre-gapped and don't bother the check them before throwing them in. The old ones could have been mishandled or met with some impact somehow, if that's what they used. New ones out of the package don't always mean they all have the proper gap, either.
Definately, a narrow gap like that would promote depositing and also a very poor spark. 0.020" is about less than half of what is needed for NA application.

 

Alright, thanks xviper.

I don't have too many miles on the new cylinder head, maybe about 25k... Do you think I would be okay just changing out that one spark plug or should I just go ahead and replace all four?

 

You should at least inspect all of them to make sure the others look OK. If they look good and in about the same condition as each other, then you're probably OK to just change the one. However, if it were me, I'd feel better if they were all the same age.

 

Alright. Thanks a bunch man.

 

Interesting, I have a weird faint ticking after my short block and valve seal replacement. They changed the auto-tensioner but the tick is still there so this might be the next thing to check. I've only put 600miles on it since the short block replacement.

 

I took a couple shots of the bad plug. Here ya go: