Error code
 

P0301 & P0303 have just come up on my 02 wrx, I know what the the fault codes are but what is causeing it, is it because i used cheap asda fuel:Suspiciou

sounds like the same prob ive got mate but im getting misfire codes on all cylinders but the cause is the nps switch on the gearbox

phil

Whats the nps switch:confused:

NPS is the Neutral Position Switch on the Gearbox........... sometimes a faulty NPS geabox switch causes the ECU to think it has an engine misfire !

The 02 bugeye WRX had a new (and very good Denso) ECU in Place of the older JECS ECU on the Classic.

Cracking ECU (Mine runs my car at 400 BHP with Methanol Injection) but it sometimes gets a bit confused LOL

I'd run it for a bit longer on Optimax and if it continues then swap the NPS switch :D

Shaun