NO.7 SLOW RETURN TO IDLE [MZR-CD (RF Turbo)]

BME010300103278

7

SLOW RETURN TO IDLE

DESCRIPTION

• Engine takes more time than normal to return to idle speed.
• Engine speed continues at fast idle after warm up.

POSSIBLE CAUSE

• Thermostat is stuck open
• Fuel injection timing is incorrect
• Erratic signal from CKP sensor
• Erratic signal from CMP sensor
• ECT sensor or related circuit malfunction
• Accelerator pedal position sensor or related circuit malfunction
• MAF/IAT sensor or related circuit malfunction
• Fuel pressure sensor or related circuit malfunction
• Incorrect adjustment accelerator pedal position sensor and/or idle switch
• Incorrect adjustment of idle speed
• Excessive fuel pressure
• Fuel pressure limiter malfunction (built-in common rail)
• Fuel injector malfunction (incorrect fuel regulate pressure)
• Main fan control system malfunction
• Neutral switch or related circuit malfunction
• IDM or related circuit malfunction
Warning
The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:
• Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
• Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injury or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE SERVICE PRECAUTION" and "AFTER SERVICE PRECAUTION" described in this manual.
(See BEFORE SERVICE PRECAUTION [MZR-CD (RF Turbo)].)
(See AFTER SERVICE PRECAUTION [MZR-CD (RF Turbo)].)

Diagnostic Procedure

STEP

INSPECTION

RESULTS

ACTION

1
Connect the WDS or equivalent to the DLC-2.
Turn the engine switch to the ON position.
Retrieve any DTC.
Is DTC displayed?
Yes

DTC is displayed:

Go to the applicable DTC inspection.

Communication error message is displayed:

Inspect for the following:
• Open circuit between PCM control relay and PCM terminal 53 or 79
• Open circuit PCM control relay and PCM terminal 69
• PCM control relay stuck open
• Open or poor GND circuit (PCM terminal 65, 85, 103 or 104)
• Poor connection vehicle body GND
No

No DTC is displayed:

Go to the next step.
2
Access ECT PID.
Start and warm up the engine to normal operating temperature.
Is ECT PID reading between 82-112 °C {180-233 °F}?
Yes
Go to the next step.
No

ECT PID is higher than 112 °C {233 °F}:

Go to symptom troubleshooting "NO.17 COOLING SYSTEM CONCERNS-OVERHEATING".

ECT PID is less than 82 °C {180 °F}:

Go to symptom troubleshooting "NO.18 COOLING SYSTEM CONCERNS-RUNS COLD".
3
Inspect idle speed.
Is idle speed correct?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the idle speed inspection results.
4
Inspect the main fan control system operation.
Does the main fan control operate properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the main fan control system operation inspection results.
5
Inspect adjustment of the accelerator pedal position sensor and idle switch.
Are the accelerator pedal position sensor and the idle switch adjusted correctly?
Yes
Go to the next step.
No
Adjust the accelerator pedal position sensor and the idle switch correctly.
6
Inspect adjustment of the neutral switch.
Is the neutral switch adjusted correctly?
Yes
Go to the next step.
No
Adjust the neutral switch correctly.
7
Visually inspect the CKP sensor and teeth of the pulse wheel.
Are the CKP sensor and teeth of the pulse wheel normal?
Yes
Go to the next step.
No
Replace the malfunctioning parts.
8
Measure the gap between the CKP sensor and teeth of the pulse wheel.

Specification

1.5-2.5 mm {0.059-0.098 in}

Is the gap within the specification?
Yes
Go to the next step.
No
Adjust the CKP sensor position.
9
Visually inspect the CMP sensor and teeth of the pulse wheel.
Are the CMP sensor and teeth of the pulse wheel normal?
Yes
Inspect the following PIDs:
• ECT
• IAT
• MAF
• RPM
If PID value is not as specified, repair or replace the malfunctioning part.
If PID value is normal, go to the next step.
No
Replace the malfunctioning part.
10
Remove the thermostat and inspect operation.
Is the thermostat normal?
Yes
Go to the next step.
No
Replace the thermostat.
11
Inspect the fuel injector relief pressure.
Is the fuel injector relief pressure normal?
Yes
Remove and inspect the supply pump and the common rail.
No
Replace the fuel injector.
12
Verify test results.
• If normal, return to diagnostic index to service any additional symptoms.
• If malfunction remains, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZR-CD (RF Turbo)].)