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Basic Idle Speed

NOTE: Basic idle speed should only be adjusted after verifying spark plugs, fuel injectors, idle air control motor and engine compression are okay.
NOTE: Basic idle speed is checked with IAC motor at standard position. Basic idle speed has been adjusted by manufacturer with speed adjusting screw. There should NOT be a need for readjustment. In case adjustment has been tampered with, manufacturer gives following adjustment procedure.
  1. Ensure vehicle is at normal operating temperature with all lights, cooling fan and accessories off. Shift transmission into Neutral or Park position.
  2. Connect scan tool to OBD-II Data Link Connector (DLC). OBD-II DLC is located below dash, near steering column. See Figure.
  3. Start engine and allow it to idle. Using scan tool, select MFI SYSTEM ACTUATOR TEST, then select item No. 30 (SAS mode or IAC motor test mode). SAS mode/IAC motor test mode sets IAC stepper motor to basic step. Check basic idle speed. See IDLE SPEED SPECIFICATIONS .
    CAUTION: MFI system actuator test must be cancelled, or test will continue to run for 27 minutes. Driving vehicle under this condition may damage engine.
    4. NOTE: If idle speed is lower than standard value on a very cold engine (-4°F) even when IAC motor is fully open, air volume limiter built in throttle body could be defective.
  4. If idle speed is too low, check for throttle valve deposits. Clean as necessary. If idle speed is not within specification throttle and throttle valve is clean, turn speed adjusting screw until correct engine speed is obtained. See Fig 1. Remove rubber plug to access speed adjusting screw, if applicable.
  5. On Diamante, Mirage and Montero Sport 3.0L, if idle speed cannot be lowered by turning engine speed adjusting screw, determine if fixed Speed Adjusting Screw (SAS) has been moved. Fixed SAS is stop screw contacting throttle lever. See FIXED SPEED ADJUSTING SCREW  for procedure. On all vehicles, cancel MFI system actuator test. Turn ignition off and disconnect scan tool.
  6. Start engine and let idle for 10 minutes. If idle speed is still incorrect, possible cause is malfunction in Idle Air Control (IAC) circuit. See IDLE CONTROL SYSTEM in SYSTEM & COMPONENT TESTING article.
IDLE SPEED SPECIFICATIONS

Application Basic Idle Curb Idle
Except Diamante 650-750 600-800
Diamante 600-800 600-800
Fig 1: Adjusting Idle Speed (Typical)
G93F78134Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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