I have been waiting for about two weeks to post this as I didn't want to jump the gun. But about a few weeks ago I decided to change my plugs to a heat range that was two steeps colder. I was under the impression that maybe the high egt's and lean a/f mixture that is normally seen when cruising was causing the actuall electorde of the spark plug to glow red and pre-ingnite the fuel causing a bad knock which then would pull timing. Also it has been noted that everyone here who has had the p0300 missfire problem has said that as soon as you let off the gas it clears out. Well by letting of the gas your egt's will drop hence cooling the plug. Well two week later and about 1500miles of road trips to Atanta(boost solutions) and I have not yet seen the missfire. So I feel safe to say that the new plugs are what fixed it.

Now for what everyone is waiting for.........................

plugs are NGK BR9EIX

hope this helps guys

 

nice, i need to run some cold plugs where did you pick them up at?

 

I had to order mine from Advanced Auto parts. Got them the next day.

 

Thanks for the post, I'm on my way to Advance to order this plugs...
hopefully this would work for my Evo...
Thanks again.

 

cool thx

▒▓▒▓▒▓▒▓

 

no problem

 

post results please guys. also, are all these evos stock?

thanks!

 

Mitsu is saying that the 0300 code most people are getting is caused by a NVH issue in the drivetrain causing the ecu to see knock....when it really is just vibration from the trans. If this is true, I'm not sure how colder plugs will fix the problem.

That is, unless there are 2 seperate problems here that are throwing the same cel.

But I am glad that changing the plugs got rid of your problem.

SC~

 

I am running 1-step colder plugs right now (denso iw24) and the "misfire" is still occuring.

The fix is in the tranny, it's already been discussed. The weather seems to have a HEAVY influence on my car's misfiring tendencies as well, < 45 degrees F out and I am misfiring all over the joint.

I say "misfire" because it's not really a misfire.

Should this thread get merged with the original?
https://www.evolutionm.net/forums/sh...ighlight=p0300

 

Doug quick question, did you notice any difference in the performance of the vehicle?
Thanks again...

 

Yes did notice that my egts dropped, and car pulls much smother. Not to be one to dobt but I can't see how NVH is the cause of the missfire. Specially when most people have the worst NVH on decell and that is when the missfire clears. To me it seems like this is just another way for them to pawn off the real problem. When I called tech line the other day they told me that they had infact found out that the trans wasn't the cause and that they were looking into other solutions at this time. I also informed them as of my fix to the problem and they said they would look into it. "webguy330i" one step colder isn't as much of a jump as too. NGK plugs work on a whole diffent scale as other plugs and its my advice to try the BR9EIX plugs for your self. I am also at around 2000miles now with these plugs in my car nothing else changed, have driven in all different weather conditions and still have yet to get the p0300 miss fire again.

 

That sounds great Doug... I'm picking up my plugs tomorrow. I will post my results after a week and for inquiring minds I'm running K&N drop in and Perrin CB. I'm having a hard time believing that the cause of the misfire code is from trans. vibration coz I usually get the SES when I'm cruzin round 70 tp 80 mph.
Thanks again for your input...

 

It was my understanding that vibration of a very specific frequency eminates from the tranny that is detected by the knock sensors as active engine knocking....it in turn alerts the ecu that it is seeing too many knocks and the ecu pops out the CEL and goes into safe mode.

In my exp with this issue, the cel doesn't clear upon decel. It clears only after the ecu has seen no more 'knocks' for a number of cycles (turn car on, drive, turn car off... equals a cycle)....it throws a cel upon slight acceleration at very specific rpm's and at very specific throttle pedal angles at specific speeds.

SC~

 

Doug, what they meant to say was that they don't want to replace anymore $4k transmissions, so they are suspending that as the "cause" of the problem.

There is no actual misfire occuring, unless your injectors are getting stuck which is possibility #2 for mitsu tech line when diagnosing the p0300 issue. Even then it's a rich condition misfire not a lean.

I still believe it's a transmission component which is causing the knock sensor to falsely alert the ecu of a non-existant condition, hence why they are doing the reflash and why they've already replaced a number of transmissions.

You guys can speculate all you want but it's hard to argue with what has already proven to be the "now" solution and pending solution.

 

Try this when my car "misfires" my A/F ratios on my in car wide band go FULL LEAN IE 20/1 + meaning the ECU is cutting the injectors out of the loop...Just one more brick in the wall of confusing DATA!