I just recently went with the Denso Iridiums and my car seems to run a bit worse. Stumbles at idle and almost stalls. RPMS are all over the place at idle. Dipping as low as 100 up to 1.5k. My question is what other plugs out there will work with a modified Evo? Basically, what is the best plug for my setup? I have a set of Champion Double Platinums that should work fine. Any thoughts? Thanks guys.

-Steve

 

I didn't believe the NGK BPR 7ES copper plugs would run smoother than the iridiums... but for less than a $10 investment, I said what the hell. At 24k I switched mine out and they really do run better. I'm quite surprised. If you've cranked up the boost, you may want to try the NGK BPR 8ES.

 

I looked into this a while back but I'm no expert. I've seen a vendor selling NGK Irridium plugs 1 heat range colder, which I would imagine is the best setup. Otherwise, you could go with copper BPR7ES (1 range colder as well) like DSMs use, and just change them more often. However, it sounds to me like either you got the wrong model plugs entirely, your plugs weren't gapped correctly, or a plug wire has be broken or mis-installed. Make sure those Densos exactly cross reference to the factory NGKs. If they do, double check the gaps. If they are gapped correctly, do an impedence test on the wires, and make sure they are clean and have a healthy dose of that grease (I think it's dielectric grease?). Also, maybe your wires are not going to the proper plugs?

 

The new plugs have NGK R1 on them. I also have upgraded plug wires to Magnecore 8mm. I put in the Champion Double Plats and I was misfiring at WOT. Got those out quick. Should have known those plugs where dookie.

 

Just go with the cheap BPR7ES NGK plugs.

 

stick with the iridium plug. 1 heat range colder should work well.

 

I tried to tell him... just because it is "cheap" does not mean they are not effective plugs... no plugs have gone quicker/faster wearing a