Join Date: Aug 2007
Location: Newberg, OR
Car Year: 2007
Car Model: Forester Sports XT
Was the front & rear O2 sensors replaced? Other then the CEL, does your '01 seem to be operating normally?
IMO, a failing "front" O2 (A/F, air/fuel) sensor will cause hesitation, back fire & sooty exhaust pipe (running rich). The rear O2 sensor is used to monitor the operation of the CAT. It won't cause your engine to operate poorly. It does tell you (CEL code P0420) if the CAT is going south, or something further upstream is not right.
My 2 cents worth.
'07 FSXT - COBB Surgeline dyno Protune - Stage 1+
'03 X +AVO turbo kit = XT (son's)
'95 Neon Sport
Last edited by 2.5x_sleeper; 04-11-2008 at 11:03 PM.
Reason: Corrected typo...