Poor Fuel Economy

Check for fuel leaks.
Check fuel quality.
Ensure brakes do not drag.
Check accelerator pedal linkage.
Ensure cooling fan system is functioning properly.
Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Check throttle position sensor circuit. See CODES 41 & 47 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Check distributor and spark plugs.
Check ignition coil.
Check engine compression.
Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
Check injector circuit. See INJECTOR CIRCUIT chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
Check fuel pressure control vacuum switching valve circuit. See FUEL PRESSURE CONTROL VACUUM SWITCHING VALVE (VSV) CIRCUIT chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
Check idle speed control valve circuit. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
Check neutral start switch circuit. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Check main oxygen sensor circuit. See CODES 25 & 26 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Check sub-oxygen sensor circuit. See CODES 27 & 29 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Ensure transmission is functioning properly.
Check valve timing, timing belt and piston rings.
Check ECU.