Poor Idling

High Idle Speed

• Check A/C signal. A/C signal may also be referred to as A/C switch signal or compressor circuit. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
• On 2001 MR2 with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
• On all models, check Engine Control Module (ECM) power source circuit. See ENGINE CONTROL MODULE POWER SOURCE CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.

Low Idle Speed

• Check A/C signal. A/C signal may also be referred to as A/C switch signal or compressor circuit. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
• On Avalon, Camry 2.2L 4-cylinder gasoline models, Camry 3.0L V6, Camry Solara, Celica, Corolla, ECHO, Highlander, MR2, Prius, RAV4, Sienna, Tacoma, Tundra 3.4L V6 and 4Runner, check fuel pump control circuit. See FUEL PUMP CONTROL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
• On Camry 2.2L 4-cylinder CNG models, check fuel shutoff valve circuit. See DTC P1190: FUEL SHUTOFF VALVE MALFUNCTION test in SELF-DIAGNOSTICS - CAMRY 4-CYLINDER - CNG article.
• On Land Cruiser, check fuel pump control circuit. See DTC P1200: FUEL PUMP RELAY/ECU CIRCUIT test in SELF-DIAGNOSTICS - LAND CRUISER article.
• On 2001 MR2 with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
• On Sequoia and Tundra 4.7L V8, check fuel pump control circuit. See DTC P1200: FUEL PUMP RELAY CIRCUIT test in appropriate SELF-DIAGNOSTICS article.

Rough Idle

• Check engine compression. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• On Avalon, Camry 2.2L 4-cylinder gasoline models, Camry 3.0L V6, Camry Solara, Celica, Corolla, ECHO, Highlander, MR2, Prius, RAV4, Sienna, Tacoma, Tundra 3.4L V6 and 4Runner, check fuel pump control circuit. See FUEL PUMP CONTROL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
• On Camry 2.2L 4-cylinder CNG models, check fuel shutoff valve circuit. See DTC P1190: FUEL SHUTOFF VALVE MALFUNCTION test in SELF-DIAGNOSTICS - CAMRY 4-CYLINDER - CNG article.
• On Land Cruiser, check fuel pump control circuit. See DTC P1200: FUEL PUMP RELAY/ECU CIRCUIT test in SELF-DIAGNOSTICS - LAND CRUISER article.
• On Sequoia and Tundra 4.7L V8, check fuel pump control circuit. See DTC P1200: FUEL PUMP RELAY CIRCUIT test in appropriate SELF-DIAGNOSTICS article.

Surging

• Check Engine Control Module (ECM) power source circuit. See ENGINE CONTROL MODULE POWER SOURCE CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
• On Avalon, Camry 2.2L 4-cylinder gasoline models, Camry 3.0L V6, Camry Solara, Celica, Corolla, ECHO, Highlander, MR2, Prius, RAV4, Sienna, Tacoma, Tundra 3.4L V6 and 4Runner, check fuel pump control circuit. See FUEL PUMP CONTROL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
• On Camry 2.2L 4-cylinder CNG models, check fuel shutoff valve circuit. See DTC P1190: FUEL SHUTOFF VALVE MALFUNCTION test in SELF-DIAGNOSTICS - CAMRY 4-CYLINDER - CNG article.
• On Land Cruiser, check fuel pump control circuit. See DTC P1200: FUEL PUMP RELAY/ECU CIRCUIT test in SELF-DIAGNOSTICS - LAND CRUISER article.
• On 2001 MR2 with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
• On Sequoia and Tundra 4.7L V8, check fuel pump control circuit. See DTC P1200: FUEL PUMP RELAY CIRCUIT test in appropriate SELF-DIAGNOSTICS article.