just buy a set of ngk's BPR7ES you can get them from murrys, see if that fix the problem, did you buy the car used or new? i would log the car and also check on the map. Also that code pops on 03 evos with cams. but you got stock cams i assume.

 

Well just to add some closure on this subject. I read somewhere here that its possible to add code to the programming that will disable the misfire test. No misfire test, no misfire correct? lol. I found a local guy who street tunes. I told him I JUST wanted to disable the Misfire test. He said he would only charge me 50 bucks. We ended up doin a street tune and he changed up my mapping just a tiny bit and it fixed it. Guess my previous tune was the problem. So after all this drama and stress. it only took me a cup of coffee, a few text messages, knowing the right person, and a couple hours of my time.

(thanks to the tuner BTW)

 

Just my 2 cents but you may be masking a problem. I had this issue a few years back. It was normall highway driving or mid-throttle crusing, it would start to shudder and correct if I down shifted or slowed down and accelerated in the same gear.

The early evo's use torrington bearings and shims in the transmission. When these bearings wear out, it causes the input shaft to vibrate. The knock sensor picks up this vibration and thinks that the engine is knocking causing the timing to retard. Thus causing the P0300 for a randon misfire.

The newer evo's use tapered bearings to put preload on the gears. I sent my trans to Jacks transmissions. At that time, it was 1400 for a full rebuild plus some goodies and I never had a problem since.

Since this was tuned out of your ECU, you may actually get spark knock and your ECU is ignoring this. You may run into problems down the road.

 

It is nice to have someone actually give a reason for why the transmission could be causing the P0300.

I as well as many others have had the P0300 disabled for years with no ill effects though. Eventually when I get my tranny rebuilt I will have to get the tapered bearings and try turning the P0300 back on.

 

Wow evolve, thats serious sh@t. How can you tell if you have spark knock? Can that knock light ( forgot who makes it) make sure i can monitor it?

 

I had this same issue.. after changing ALL the plugs and wires I was still missing/getting the code. I did EVERYTHING common sense would tell us to do, but I took it to road race engineering and they dyno tuned it for me, then they disabled the p0300 check in the computer.

Don't run full boost while that code is on. Car runs like crap.

get it tuned. Theres supposed to be a dealer "fix" for this by flashing the computer but it doesn't work.

 

Usually the computer sees knock through the knock sensor or crank/cam signal. If you take away the parameter for the ecu to see knock, you may blow the engine. That's typically after its modded.

 

So basically Id see my check engine light go on ir If I check my fault codes I can see it.

 

Disabling the P0300 will not stop the engine from seeing knock. It only disables the code for the P0300. After that point the car never goes into the limp mode caused by the P0300. I have used the Tephra mods to make my check engine light flash if knock is registered.

Also disabling the P0300 will not stop the car from throwing specific cylinder miss fire codes P0301 through P0304.

 

The tuner said he changed some fuel mapping numbers and it fixed the problem.