Review on Premium Performance Upgrade: 6 New NGK Iridium IX Spark Plugs LFR5AIX-11 # 4469 by David Carter

These were recommended candles. All were neatly ironed. Oddly enough, when I changed them out, I noticed that some of the old spark plugs weren't tight enough, which caused some oil to leak out. Clean well before installing new spark plugs. You can also apply some dialect grease around the connector. If your car has 100,000 miles or more and you haven't changed your ignition coils, you should do this when you change your spark plugs since you are already pulling out the coils. Getting to the outlets isn't difficult, so do both while you're there. It would probably be nice to do the wiring harness too, but I didn't. I ended up replacing the spark plugs because my Z was working really hard. Bad coil came in #1. A good mechanic has a coil reader and can tell you what's bad. I suspect a multimeter could give you some readings. I am not sure. YouTube it. Save time and money by taking other preventive measures like O2 sensors. You don't want to kill your cat. Take a mass air flow cleaner and clean it. It's easy to get to.