Subaru Legacy Outback was purchased new in1999. It has been maintained faithfully, and has had very few problems up until 2011.

First indication of a major problem was at 243,214 miles in November, 2011 when the MIL came on and gave the code of P0303 (misfire in cylinder 3). Local mechanic diagnosed a burnt valve. Engine was replaced with a rebuilt engine. Problems began arising again on 10/17/12 with codes P0301 and P0302. Since that time, the vehicle consistently throws the codes P0301, 0302, 0303 and 0304 (not altogether) when ever the vehicle goes over 65 MPH a day or so later after the codes have been erased.

The original mechanic has spent days (mostly on his own time) trying to find the problem as has the local Subaru dealer. As part of the attempted repair the engine has been back to the rebuilder (in Colorado) three times. Things replaced include ignition wires (twice), neutral safety switch, ignition coil, belts, engine pulley, crankshaft and camshaft sensors, valve adjustment(s), an EGR inspection, EGR valve, ECU, fuel pressure regulator, fuel pump and throttle position sensor. Switched out and tried different a MAP sensor, EGR vacuum modulator, Air mass sensor, vacuum switching valve and the ignitor. Replaced vacuum lines, O2 sensor, injectors 3&4, cleaned the throttle body, and squeezed female connectors. Nothing has worked.

Certainly having the light on is annoying, BUT the big problem is that in California having the MIL light on is an automatic SMOG certification failure. There are ways to "game" the system to pass, but that doesn't solve the basic on-going problem, and having an MIL system that works correctly is vital for future engine/car malfunction diagnosis. Has anyone else had this kind of problem?