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

id0103d2801300

7 | SLOW RETURN TO IDLE
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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
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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].) Are there any DTCs displayed? | Yes | DTC is displayed: • Go to the appropriate DTC inspection. (See DTC TABLE [MZI-3.7].)
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.
No | Go to the next step.
3 | Is the throttle body free of contamination? | Yes | Go to the next step.
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].) Does the PID indicate the correct values according to the steering wheel position? | Yes | Go to the next step.
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.
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].)