Do you gap your plugs?

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I've always checked and, if necessary, gapped spark plugs that I was replacing. I've heard recently that plugs come pre-gapped... this sounds a bit ludicrous to me if only for making the assumption that the factory got it right for your specific application.

Thoughts?
 
I have always checked them. Mostly all good, but it is so simple, why take the chance that they may have been dropped or something. Although with as many plugs as i have checked/gaped over the years, i can tell by looking within a few thousands if they are correct.
 
The times that I've changed iridium plugs in recent years, the plugs were within the spec'd gap range for each vehicle so I didn't have to bother with it. I'm assuming that's now the norm for most applications unless you're tweaking them for a particular reason.
 
Nah. The NGK plugs come pre-gapped and have a protective sleeve on the electrode, so the gap stays in spec from the factory to my car.
 
Originally Posted By: fenixguy
I always check before installing. I've never had to gap one.


I've had to gap a few over the years. It is most likely because somewhere from where they were made to where they were sold someone probably dropped one. It doesn't hurt to check, then use care if you have to gap one.
 
It might be worth a check especially if you spend all afternoon standing on your head and having to do major surgery to get to those back plugs. The person that designed some of these vehicles with plugs that are next to impossible to reach should be forced to post his name and email address so that people can return the favor.
 
I changed the original plugs out of a Ecotec Malibu and the gap had grown from .043" to .090" and they were working just fine. Put in new OEM double iridium plugs that came gapped at the factory spec. In my experience, plugs last almost forever now.
 
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Many precious metal plugs say do not gap as the thin electrode and tiny ground puck are somewhat fragile, you can actually do more harm than good just checking them. I eyeball them for obvious damage or one that looks off from the others and I do check non precious metals. Many missing pucks and misfires an be directly attributed to being gapped. Just one example...

Quote:
Gaps should never be adjusted on the OE-Fine Wire Platinum. Bosch OE-Fine Wire Spark Plugs have factory pre-set gaps, and should never be gapped by the installer.
 
The last two sets of plugs I put in my car were supposed to be pre-gapped.

On one set, 2 of the 4 were undergapped (.044 instead of .051)
On the other set, all 4 were undergapped.. by even more.

I ALWAYS check.
 
I think NGK changed their stance a bit on gapping platinum and iridium plugs. They now say it's OK, but only use a wire gap tool's puller and don't force anything. I think the bottle-opener style puller on a tapered regapping tool isn't the kind you want to use.

Quote:
https://www.ngksparkplugs.com/about-ngk/spark-plug-101/5-things-you-should-know-about-spark-plugs

In the late 1980s, when fine-wire spark plugs first appeared, installers used incorrect gap tools and procedures resulting in bent or broken-off firing electrodes. As a result, many people assumed that one cannot adjust the gap on a precious metal plug. While most NGK spark plugs are pre-gapped, there are instances where the gap requires modification. NGK recommends a wire-style or feeler gage gap tool, which can adjust the gap without prying against the center electrode. NGK also recommends adjusting the gap no more than +/- 0.008” from the preset gap.


There shouldn't be anything inherently bad about regapping a platinum plug, but I guess a lot of people just did it the same way they used to and ended up chunking off the tips. Scratching a nickel alloy electrode isn't likely to affect the performance of the plug. Scraping off the platinum tip will.

Denso says use needle nose pliers or a gap tool, but be careful not to touch the center electrode or the porcelain. I think one issue with these thin-wire electrodes is that there's also not much between the ground electrode and the porcelain, so it's easy to damage the porcelain.

http://densoautoparts.com/spark-plug-installation
 
"Trust, but verify!" is my stance on plug gap (especially new plugs). I will use the flat feeler gauge NGK approach if needed to adjust them.
 
Originally Posted By: SirTanon
The last two sets of plugs I put in my car were supposed to be pre-gapped.

On one set, 2 of the 4 were undergapped (.044 instead of .051)
On the other set, all 4 were undergapped.. by even more.

I ALWAYS check.

Denso claims that the performance of their iridium plugs can make up for slight differences in factory-set gap. I'm a bit skeptical, but that's what they claim. Some people claim that standard plugs with nickel alloy electrodes actually run better, but of course won't last as long since the electrodes wear down. The precious metal electrodes of course fire through the thin wires, so I guess that prevents erosion of the nickel alloy around the thin wire.

I remember on my 1995 Integra GS-R the specified gap was a rather large 1.3 mm. I heard something about it running really hot as a result, and substituting standard plugs wasn't recommended.
 
Gotta check 'em. Decide as needed. Go back to the store if necessary.

I remember my pal went to auto school in the early '70's and many-a-plug was pre gapped even then.
 
Always.

Have bought 6, 3 were right and the other 3 ... were right for someone else. Has happened numerous times over the years. Best to be certain.
 
Yes I always check them because plugs are gapped for the most popular application, but that same plug could fit many other engines that require a different gap.
 
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