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- 2003 Mazdaspeed Protege 1660, 2004 Winning Blue RX8, 2005 Mazda6
I developed a misfire only when under boost, but the ECU wouldn't pick it up and cause a MIL, so even though the plugs had 6k on them I decided to replace them. When I removed them there was no sign of damage to the ceramic or worn electrodes. There was evidence of blow -by betwern the ceramic and the collar. I installed a new set of NGKs and the car ran awesome. And its been that way for the past three days, but tonight it started it again. This is my fourth set in 30,000 miles. The first set I replaced with platinum s, but switched them out for v-power NGKs. The V-Powers lasted about 15k miles and I developed a misfire after runningthe car hard on The Dragon and it causes the MIL to illuminated. I replaced all 4 . The bad plug had a crack in the ceramic. I went with the same plugs and they've lasted about 10,000 miles, then thyself when I started getting the misfire under boost. I went with a plug one heat range colder hoping this may help, but like I said they only lasted 3 days. I have new coils, new wires, new boots and I applied dialectric grease to them. Im currently running 12psi and have a custom tune on my SSAFC running low 11s above 4k and 10.4-10.7 up to that point. The plugs don't look to be damaged or worn at all, but corrects my misfire under boost. I have multiple ASE certifications, have been doing this professionally for 10 years and I can't seem to figure out the cause. Does anyone have any insight into this. Im going to go with Densos this time because its perhaps an issue with the NGKs only. I've always used NGKs in everything I've owned and my customers cars and I've never had this issue before. Any help is greatly appreciated because this is really bothering me. I don't care if I have to keep changing plugs every 5k, I just want to diagnose the cause of the premature failures.
