Going to pick up some new denso iridums and am wondering if I should go one step hotter here in Colorado. Thinking that stock isn't combusting enough but would like some user experiences, or just the right answer. TIA.

What vehicle is this for. And what circumstances warrent the use of irridium plugs in your ride?

I don't know about the heat range, but have you considered the NGK iridiums? Those are known to work fine in Subaru's, which can be fussy about plugs and wires. Buffalo here, which is pretty cold in the winter, stock heat range seems to work fine.

I don't know about the heat range, but have you considered the NGK iridiums? Those are known to work fine in Subaru's, which can be fussy about plugs and wires. Buffalo here, which is pretty cold in the winter, stock heat range seems to work fine.

Well, the heat range is a factor because it has been so hot here in Colorado recently. I have a feeling that these plugs are done (most likely just fouled) but considering what a pain in the rump roast it is to do the plugs on the '99 2.5L, I may as well just spring for new plugs. I know the Denso's work, they're a little pricey, but everything I've heard has been very positive. Everytime it's hot, like 130 in the sun in a black car, I throw a knock code. No big deal right? Just disco. the neg. batt cable, hold down the break for about fifteen sec., then let it sit for about 15 mins, reco. the negative, and voila... No more 325. Pulled the knock sensor and it looked fine. The fact that it resets and doesn't return when started, makes me think it's the plugs. I can feel it bog itself down when driving at "warm up idle". My theory is that it's not combusting enough fuel and causing an occasional ping or knock that sets off the CEL.

 

All too aware of the Subie's plug pickiness. Made the mistake of first installing some Bosch Plat +4's. Didn't take long to throw 301,303 codes. Replaced with stock NGK's and have been using those since.

 

What's crazy, is that I am seeing ALOT of people on the board asking gas related questions. I am wondering where they're from, octane and chain of gas station. Wonder if extra ethanol is making it's way in, or if everyone's just using 85 they way i had been... I want answers.

Sounds good. Plugs would not cause the knock sensor code you are getting. The knock sensor code indicates a problem with the knock sensor circuit. It does not mean the ECU is detecting knock. The knock sensor can look fine but still have issues.

Indeed. The knock sensors on my mom's 98 Legacy looks absolutely perfect. But throws the code for it, not always. And not imediately if I clear the ecu. But a replacement is in order.