P0301 Subaru - 2005 Forester 2.5X

Question

Engine warning light is intermittent - comes on and stays on for days, goes off and stays off for days! Sometimes responds to filler cap adjustment.

Answer 1

The problem might be spark or fuel related. as a first step replaced the spark plugs as a tune up if you have not done so (with the OEM spark plugs) and use a good fuel system cleaner like 3M and use 91 octane from sell.

if problem is still there you can try to swap the ignition coils from cylinder 1 to 3 reset the code and drive the car and see if the code comes back with P0303, if it does the igntion coil will need to be replaced.

see picture below