Car did not pass Emmisions Test.3rd and 4th Cylinders showed miss firing . on 1998 Subaru Forester

Check engine light always on.Car has all new plugs,wiring,Tune up.2 years on rebuilt engine.Good running engine.No loss of Engine Power.New oil Change.All new Belts and hoses.New Radiator.New AC .5 Speed all wheel drive.Doesnt burn Oil.There however seems to be less Mileage per Gallon of Gas.New Tires

by in Tucson, AZ on September 25, 2013
1 answer
ANSWER by on September 25, 2013
Lots of different things acn cause missfire codes. Vacume leaks, weak ignition coils, fuel injector problems and more. These engines are ifamous for exhaust valve problems. Running compression test or by removing exhaust manifold so the valves can be inspected to determine if thats the problem.