NO.7 SLOW RETURN TO IDLE [MZI-3.7]

id0103d2801300

7

SLOW RETURN TO IDLE

DESCRIPTION

•  Engine takes more time than normal to return to idle speed.

POSSIBLE CAUSE

•  CHT sensor malfunction

•  Thermostat is stuck open.

•  Erratic signal from PSP switch

•  Throttle body malfunction

•  Air leakage from intake-air

7	SLOW RETURN TO IDLE
DESCRIPTION	• Engine takes more time than normal to return to idle speed.
POSSIBLE CAUSE	• CHT sensor malfunction • Thermostat is stuck open. • Erratic signal from PSP switch • Throttle body malfunction • Air leakage from intake-air

Diagnostic procedure

STEP	INSPECTION	RESULTS	ACTION
1	Turn the ignition switch to the ON position (Engine off). Retrieve any PCM DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7 (PCM CONNECTOR (2 TYPES))].) (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7 (PCM CONNECTOR (3 TYPES))].) Are there any DTCs displayed?	Yes	DTC is displayed: • Go to the appropriate DTC inspection. (See DTC TABLE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].) (See DTC TABLE [MZI-3.7 (PCM CONNECTOR (3 TYPES))].)
1		No	No DTC is displayed: • Go to the next step.
2	Is air leakage felt or heard at intake-air system components while racing the engine to higher speed?	Yes	Repair or replace the malfunctioning part according to the inspection results.
2		No	Go to the next step.
3	Is the throttle body free of contamination?	Yes	Go to the next step.
3	Is the throttle body free of contamination?	No	Clean or replace the throttle body. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [MZI-3.7].)
4	Access the PCM PID PSP using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7 (PCM CONNECTOR (2 TYPES))].) (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7 (PCM CONNECTOR (3 TYPES))].) Does the PID indicate the correct values according to the steering wheel position?	Yes	Go to the next step.
4		No	Inspect the PSP switch and related wiring harnesses. (See POWER STEERING PRESSURE (PSP) SWITCH INSPECTION [MZI-3.7].) Repair or replace the malfunctioning part according to the inspection results. • If the malfunction is remains, perform the intermittent concern troubleshooting procedure. (See INTERMITTENT CONCERN TROUBLESHOOTING [MZI-3.7].)
5	Cool down the engine. Remove the thermostat and inspect the operation. (See THERMOSTAT REMOVAL/INSTALLATION [MZI-3.7].) (See THERMOSTAT INSPECTION [MZI-3.7].) Is the thermostat normal?	Yes	Inspect the CHT sensor. (See CYLINDER HEAD TEMPERATURE (CHT) SENSOR INSPECTION [MZI-3.7].) Repair or replace the malfunctioning part according to the inspection results.
5		No	Replace the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION [MZI-3.7].)
6	• Verify test results. ― If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZI-3.7].) ― If malfunction remains, inspect related Service Information and perform repair or diagnosis. • If vehicle is repaired, troubleshooting completed. • If vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZI-3.7].)