My non turbo 740 was running ok until one morning-fired it up and it ran really rough,almost insufficient power to drive off.It was well overdue for a service,so changed plugs,plug wires,distributor cap,rotor arm,fuel filter,air filter,and cleaned pcy filter/flame trap.This made no difference,so checked all vacuum hoses,cleaned throttle body,reset low idle screw and throttle switch,checked harness connector at AMM,and finally fixed the misfire by replacing the air inlet hose,which was badly perforated.However,fault codes 231,which had been there all along,and fault code 113,which was occasionally there,still flash up.I still have a low idle of 1500 rpm which kicks in about 10 to 30 seconds after start up.The low idle motor seems to work ok .Any ideas before I replace the O2 sensor or ecu?