Same thing was happening with me. I didn't want to drive the car on the hwy ever! Every 5 sec it would vibrate/misfire.

What plugs and gapping are you running? I had Iridiums when I had the issue, but guess they got messed up, cause whatever gapping I tried to set, it still continued. I probably messed up the electrode since I heard they are sensative. Finally switched to the basic BR8ES (colder, yes), with a .022 gapping and don't have the issue anymore. Try it. You probably can even try the BPR8ES or BPR7ES gapped at about .024. See what happens then and keep us informed.

 

If i ever decide to rebuild my tranny with Shepard Racing or TRE do i have to tell them that I have an 03 Evo with a P0300 code problem? or do they automatically replace the input shaft with an updated part along with the input half of 5th gear as part of their tranny rebuild?

 

Well I have an update, I purchased a creader. It does help but doesn't cure it. Instead of having a misfire/studder 100+ times on the interstate in an hour, it will do it once. I clear the code, and it stops. However it will still misfire/throw the code about 4 times in an hour on the interstate.

I also noticed now that my car will throw the code/studder in third and fourth gear if I am getting off the interstate after an hour or so.

It won't do it around town, or 30 minutes or less on the interstate.
I changed my plugs recently. I already had bpr7es in which is what I kept. I gapped them at .26
I am going to try the colder plug 8es and gap it a little smaller.

Will this hurt my performance at all? Should I try the 7es at a smaller gap ex.. .22 or so?
Any thoughts. BTW my car just hit 49k, but has been doing this since 33k. I know my warranty is up but I am supposed to have some kind of 60k warranty right?
Will any dealership consider honoring a warranty and replace the input shaft/rebuild my tranny? Otherwise how much is it for a shep rebuild?

 

Any updates on your situation Gsxtremedsm? I have a similar, if not the same problem. Here are a couple other threads with the same kind of issues:

https://www.evolutionm.net/forums/sh...d.php?t=256581
https://www.evolutionm.net/forums/sh...d.php?t=261958

Anyone have a solution.... or rather, anyone actually experienced this and corrected the problem? ...or know of anyone that corrected the problem?

 

it is the coil pack! i tried changing wires, plugs and it still misfiring till i change the coil pack!

 

+1 on the coilpack

 

i recently got this code after my hks 280s went in.

i think because im untunned and the idle is so lumpy the code trips

 

by coil pack, are you referring to the stock coil caps?

 

yup! replace it or do a test first using analog meter then from there you will know if its your coil pack or your wires!