Spark plugs?
 

I have a 2003 nissan 350z it has less than 52000 miles and I have had no issues until I changed from the stock spark plugs to the NGK iridium spark plugs. Now I'm getting some type of knocking noise I pulled out the spark plugs and they have a black ring around them which I don't know if it's good or bad. The check engine light isn't on but What do I need to do to fix these problems?

This falls into the category of "If it ain't broke, don't fix it." Put the old plugs back in, and see if the problem persists. Go from there.

When doing spark plugs, ALWAYS go OEM.

Alrighty thanks guys!

What is the gap supposed to measure?

NGK laser platinum , that is what you want. Even though the iridium thing was the hot thing for the ricer market over the past 10 years

DO NOT GAP PLUGS

The precious metal used on the plugs is a very thin layer. by gapping the plugs u will effectively be "sanding" platinum, or iridium off.
They come pre gapped. be happy.

Actually you should still check them. Once an a while you get one way off , banged up in transit.

^ +1 on checking the gap

I've always used NGK coppers and never had any issues. Platinums will last longer, though.

you are not supposed to change spark plugs untill you hit 105k miles

I believe they are 60k , but may be different between different year cars

I think tomorrow I'm going to change the old ones back the iridiums aren't working for my car -__- ill just take the loss on the $54 I spent

LOL, not supposed to???

That is what the manufacturer says to sell cars. just like never needing to change transmission fluid. (bmws joke)

If you do not change your plugs until 100k you risk the chance of it being seized into your head. Ford is notorious for this, a quick google search will show you how bad it is with ford. for 50 bucks change your plugs every 30-40k. if you plan on having your car for along time whats 150$ for a few plug changes vs have to pull the top end of the motor apart to repair the busted plug!
My buddy (ase certified) tech, was doing a plug change on a honda, busted a plug in the head, its 4 so much easier and cheaper to fix than our cars, but why would u ever risk this to save 50$? if it requires more than 27ftlb to remove the plug u are in danger!

ALSO if you must check your plug gap, do not use the coin sized slider... use a smooth feeler gauge.

i got to be in an 4 hour lecture by NGK about spark plugs. They say do not gap them. so if NGK says it, ill live by it.
But hey, if u know better than the manufacturer, by all means gap away!

your friend is wrong 105 is the magic number

^ You're not entirely correct, either. It's not that you're "not supposed to change plugs until 105K miles," but the recommended interval before changing out the stock plugs. You can change them before then and you probably should. Think about it logically. It's like changing your oil before the service date/interval.