So I recently changed my stock spark plugs on my IX to the recommended 1 step colder Denso IKH24s gapped to .22 ; the car runs/pulls fine.

The problem is on the coldstarts, I turn the car on and it idles at 1500rpm upon startup for a few seconds then idle dips to 500rpm then stalls. I installed my stock plugs back in ( gapped .22 also) and the car idle'd perfectly fine.

Any ideas as to why I'm encountering this issue? My mods are just the simple : Exhaust/intake/3.5 fmic/255 walbro/ hallman mbc/tuned @ 24psi . Boostleak test was performed prior to tune 2 weeks ago and I found that one of the injector seals was leaking but didn't replace them till AFTER the tune due to the seals not arriving in time.

Guru's please chime in if you can

 

So I got home from work and regapped the Denso 1 step colder and just went ahead and installed them to replicate the cold idle stall to my tuner, to my surprise the car idled fine lol. I will start the car again tomorrow and see what happens, all I did after work was regap a bit

 

You don't need colder plugs on the IX. They are already specialty long reach plugs that are less detonation prone than the Evo 8

 

its been my experience that the 1steps colder foul by far faster then stock and i have had more starting and wot issues on them then stock plugs.

the 140 dollar plugs lasted me 3 months. and my stock plugs lasted 4 yrs. and even went back in the car once the other fouled til i bought new stock plugs. just my experience.

 

After reading all of your responses I feel motivated to just get rid of these and throw back in my stock plugs. My only concern now is if my tune will be affected in any way, due to the fact I was tuned this past tuesday on the 1 step colder plugs.

 

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I would say throw the stock range back in, your only at 24 psi also.

 

I'm about to do that and see how it goes

 

I went a step colder and the car just never right since, can't explain it. went back went back to stock plugs but I also drive an 8, so I don't know how much this would explain.

 

you running 93 or e85?

 

I went two step colder $180 set of four race plugs for my application. Performed flawlessly for the initial road tune. Second cold start they fouled out. We put a fresh set of stock IX plugs back in and they are performing flawless except now I have a tiny tiny bit of a knock up top that wasnt there before.

Going to try one step colder this time and see how that goes for the knock.

 

What about for a 9 2.3 hta86 running on 93 and e85, with an AEM ems 2? Made 700 on buschurs dyno, but after two pulls started breaking up. Should I try one step colder? And what gap should I be running with a cdi ignition