Iridium Spark Plugs - to gap or NOT?


#1

So it’s time to change the plugs on my 02 Camry 4-cylinger. The owner manual says Denso or NGK Iridium plugs. I nab a four-set of NGK Laser OE spec Iridium Plugs. The o. manual says a .043 gap so I check them with my feeler guage and note they are off - just a tad; I adjust the gap a bit farther being careful not to abrade the electrode surfaces.

As I remove the plastic hood covering the engine for access to the plugs I THEN SEE a notice on the valve cover that says use iridium plugs, but DON’T GAP THEM.

Clearly my purchased plug gaps were narrower than spec - if only a couple of thousands. But, am I safer leaving a gap that appears to be within a 2/1000, or should I set them dead on?

Are these plug notorious for easy damage or is it some other reason the notice would say not to gap them?

And if the gap is narrower than spec should I avoid widening it because it grows wider with use? What do I do if the gap is WIDER than o. manual spec?

All thoughts appreciated.


#2

Here’s some tips.
http://www.densoiridium.com/installationguide.php

A pair of spark plug gapping pliers is by far the safest way to gap plugs, no matter if they’re Iridium, Platinum, or copper core.

If they’re within .002 and you don’t have the gapping pliers (few people do but they’re inexpensive) then I would leave them alone due to the cost of Iridium plugs. One plug probably costs more than the gapping pliers.
Hope that helps.


#3

They recommend not gapping them because the irridium center electrode is more brittle than most metals and can be fractured or broken.

The ground electrode (the hooked one) is actually platinum and can be bent carefully, but to be honest I’d just leave them be. They should be preset.


#4

I don’t bother to check them unless one looks to be really off. Gap used to matter more when we had weak ignition systems. Plugs were $.85 then and worth every penny.


#5

The recommended gap for a spark plug is not a precise figure, but simply the midpoint of a preferred range. A difference of a few thousandths ought to fall well within that range. In other words, your plugs are currently correctly gapped. BTW, note that the gap increases with use due to loss of metal.


#6

I always check. Maybe because I’ve been burned a few times. I’ve seen the gaps well out of spec at times…Rare, but it does happen.


#7

I found all replies very helpful, particularly link provided by ok4450. I’m much more enlightened. Thanks all.

Glenn D.


#8

This is what the pliers look like if you’re interested.
http://store.summitracing.com/partdetail.asp?part=sum-900313

I’m not certain but if you’re ever interested in a pair of those I think they can be gotten for less at some auto parts houses like AutoZone, O’Reillys, etc.
They work very well without breaking things and last forever. I think the pair I have has been with me for about 30 years or so and praise be; no one has walked off with them yet! :slight_smile:


#9

The gap specification can not be an absolute. It is 0.043 ± something. The plug manufacturer (or auto maker) should be able to tell you what the tolerance is. If the plugs you buy are out of that tolerance, return those plugs and get other ones. If they are supposed to be delivered with a specific gap, why fool with them?

2/1000 is less than 5% so I would think that is fine. The gap only gets wider as the plugs are used.


#10

If the plugs you buy are out of that tolerance, return those plugs and get other ones. If they are supposed to be delivered with a specific gap, why fool with them?

Because it’s a LOT EASIER fooling with them then driving 5 miles back to the parts store for replacements…Especially if they had to special order them in the first place.