I have a 2006 R Sport 2l. Has a flat spot/missfire at 2k-3.3k on medium or heavy throttle. Above 3.3k it's perfect.
Strangley if I reset the ecu and let it idle for 20 mins then drive it, it will drive perfectly for about 7 miles and then the problem starts again..
Question being, what typically will the ecu alter in the first 7 or so miles driving? Does it typically start lean and go rich? Start with retarded ignition and go more advanced? Trying to figure out what to target... I figure it can't be anything mechanical or it wouldn't be possible for it to run so well after reset.

So far I have done:
oil service
air filter
fuel filter
cleaned egrs
cleaned throttle body
changed maf
changed knock sensor

Any help really appreciated.

Oli

 

why change knock/maf sensors unless they were broken? If you believe it's an issue with the ECU/corrections then best way forward is to get it plugged in and log what's happening. The ECU setup is similar to other subarus where you have a base timing after a reset and it moves up/down from there. If it has to remove enough timing then you get a load of extra fuel through as well as reduced timing.

Most likely guess so far is the misfire is causing the ECU to retard timing which results in no power on top of whatever fault you have mechanically - be hard to narrow it down without some diagnostic data though.