A FEW DAYS AGO DURING MORNING START UP CHECK ENGINE LIGHT LIT UP. AFTER SCANNING FOR CODES IT SHOWED P0170 FOR "FUEL SELF ADAPTATION AT IT'S LIMIT" OR SOMETHING LIKE IT... I RESET THE CODE AND AFTER FOUR DAYS I HAVE THE SAME PROBLEM. THE FRONT O2 SENSOR WORKS OK ON HOT ENGINE, REAR O2 IS KIND OF "SLOW" WHAT DO I DO CHANGE MASS AIR SENSOR ? IT'S EXPENSIVE!
PS. P0170=LEAK IN INTAKE AIR,FUEL INJECTORS OR EVEN WORN ENGINE, BUT NOT AT 37K.