Poor Idling

High Idle Speed

• Check A/C compressor signal circuit. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
• Check ECM power source circuit with ignition on. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED) under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.

Low Idle Speed

• Check A/C compressor signal circuit. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
• Check fuel pump control circuit. On all models except LX470, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. On LX470, perform DTC P1200: FUEL PUMP RELAY/ECU CIRCUIT test in SELF-DIAGNOSTICS - LX470 article.

Rough Idle

• Check engine compression. See BASIC DIAGNOSTIC PROCEDURES article.
• Check fuel pump control circuit. On all models except LX470, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. On LX470, perform DTC P1200: FUEL PUMP RELAY/ECU CIRCUIT test in SELF-DIAGNOSTICS - LX470 article.

Surging

• Check ECM power source circuit with ignition on. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED) under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
• Check fuel pump control circuit. On all models except LX470, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. On LX470, perform DTC P1200: FUEL PUMP RELAY/ECU CIRCUIT test in SELF-DIAGNOSTICS - LX470 article.