Symptom Checks

Perform the following:

• If engine idle is no longer rough, perform Key On Engine Off (KOEO) Self-Test. See step 1) of DIAGNOSTIC SUB-ROUTINES.
• If engine idle is rough, perform KOEO Self-Test. See step 14) of DIAGNOSTIC SUB-ROUTINES. If continuous memory Diagnostic Trouble Code (11/111-10-11/111) was NOT displayed during KOEO Self-Test, perform appropriate CIRCUIT TEST in TESTS W/CODES article in the ENGINE PERFORMANCE section.
• Check RPM drop using step 2) of CIRCUIT TEST S, or power to MAP/BARO sensor using step 3) of CIRCUIT TEST S. See TESTS W/CODES article in the ENGINE PERFORMANCE section.
• Check ignition system. See IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section.
• Check idle speed. See IDLE SPEED in ADJUSTMENTS article in the ENGINE PERFORMANCE section.
• Check fuel delivery and fuel pump. See FUEL SYSTEM in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section.
• Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section.
• Ensure engine operates at normal operating temperature.
• Check Exhaust Gas Recirculation (EGR) system. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section.
• Check engine mechanical condition. Check compression, camshaft, valve train components, intake manifold, manifold gaskets, etc.
• Check air injection. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section.
• Check air intake system. Ensure throttle plate and linkages operate properly.
• Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section.
• Check charging system.
• Check for restricted exhaust system.
• On Ranger 2.3L and all 4.9L vehicles, go to step 30) of CIRCUIT TEST KM in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section.