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We got this '98 Civic a few months ago and it had copper plugs that were worn to the nibbies. So going on the "common wisdom" that if copper was OK, platinum would be better, and Iridium would be super duper, I put in a set of Iridiums.

Then about a month later, some Facebook friends said "no no", the manufacturer says copper only. So I threw in a copper set. But it hasnt been running as well since.

Then I remembered, that platinum and iridium come pre-gapped, but I used to have to gap copper. ( but didn't with these )

Do modern copper plugs need to be gapped, or do they come pre-gapped too? DO I need to pull them and gap them? ( I still have the little tools from years ago. )

 
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Yes copper plugs still need to be gapped.

I don't see why iridiums would hurt the car?!?

I thought I had to gap my iridiums also, it's been a while.

I know Bosch makes plugs that need to be gapped but I don't like the idea of that.

 
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Ha. You don't gain performance or mileage with them, you just gain longer replacement intervals.
IMO it's overkill for a car with plugs that are so easy to replace.
Copper plug change interval is every 30,000 miles. Platinum and Iridium intervals are 60-100,000 miles (or whenever an oil burning engine manages to foul one out) and really could actually outlast the car because the precious metals generally wear so little the gaps don't open up like copper plugs do.


NGK plugs and DENSO plugs are pre gapped at the factory and have tough little round sleeves to protect the electrodes during shipment, but they should still be checked prior to installation just in case someone kicked it really hard or threw them on the floor.

Not many other brands ship this way, I really can't think of any others that do right now.
ALL plug gaps should be checked prior to installation.

NGK plug numbering: The last numbers are the gap
If the last numbers are -11 (like on PZFR5F-11 for example), the plug gap is set at 1.1mm.




You can adjust the gap on a copper plug by twisting the gapper wheel without much fear of seriously damaging the electrodes.












Platinum and Iridium can have the gaps adjusted if necessary BUT you cannot just use the little gap wheel to pry the gap apart, you will damage the preciou$ metal fine wire tips. (I do not trust using the little beveled hole in the gap wheel)

There are tools for bending the ground electrode to adjust the gap on these, and most old style wire type feeler gauges I've ever seen used to come equipped with it.

 
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The iridiums I've bought said not to try, that they were pre-gapped.

The theory is that copper conducts better, but it seems like electronic ignitions would make it where that didn't much matter?