Shrinking spark plug gaps.

[TallGuy]

Ok super weird. Other than obvious signs of rods or piston movement...I don't hear any clapping or knocking... What other factors can lead to plug gaps shrinking from .035 to .031 within a couple of weeks weeks?

I've been going through my TJ and tuning up different systems. Swapped out the plugs with NGK V-Power Nickel Plugs (ZFR5N). They're pre-gapped to .036 although I checked the gaps prior to installing and they were at .035 per my feeler.

Had some misfires recently so I just wanted to check out what whas going on inside. Popped off the plugs to see if they were telling me anything and I checked the gaps again. Totally surprised that my reading was a tight .031 and shocked that .004 would shrink off in a matter of weeks.

Plugs seemed normal. No crazy carbon or uneven markings, for 2 weeks old plugs that is. A couple were a tiny bit moist.

I'm still getting a misfire and occasional stall at about 2000 rpms, (intermittent stall) but I suspect the CPS and TPS are due. (Currently throwing p0320 and p1596)

Are the diminishing plug gaps concerning right now? I plan to recheck in a few weeks.

 

[JKP]

The only way a plug gap decreases is by contact.

If they were all the same, are you sure you measured them correctly the first time? Unlikely they would all get regapped the same by the pistons.

 

[TallGuy]

The only way a plug gap decreases is by contact.

If they were all the same, are you sure you measured them correctly the first time? Unlikely they would all get regapped the same by the pistons.

Well that's perplexing. I'm fairly certain the gaps were all 035. Even if my gauge is some how wrong, the same gauge couldn't fit inside the gaps when I checked them today. Thanks for confirming. I suppose I'll have more clues next time I check them.

 

[macleanflood]

I wouldn't discount something wrong with the NGK plugs.

Try the Autolites for kicks and giggles.

-Mac