NO.7 SLOW RETURN TO IDLE [MZ-CD 1.6 (Y6)]


B3E010318881W71

7

SLOW RETURN TO IDLE

DESCRIPTION

• The engine takes more time than normal to return to idle speed.
• The 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
• Idle switch or related circuit malfunction
• MAF/IAT sensor or related circuit malfunction
• Fuel pressure sensor or related circuit malfunction
• Incorrect idle speed
• Excessive fuel pressure
• Supply pump malfunction
• Fuel metering valve malfunction
• Fuel pressure limiter malfunction
• Fuel injector malfunction (incorrect fuel regulate pressure)
• Clutch pedal position switch or related circuit malfunction
Warning
The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before servicing the fuel system:
• 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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.

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.
Are DTCs displayed?
Yes

DTC is displayed:

Go to appropriate DTC test.

Communication error message is displayed:

Inspect for the following:
• Open circuit between PCM control relay and PCM terminal 236 or 231
• Open circuit between PCM control relay and PCM terminal 241
• PCM control relay stuck open
• Open or poor ground circuit (PCM terminal 307, 308 or 332)
• Poorly connected vehicle body ground
No

No DTC is displayed:

Go to the next step.
2
Access the ECT PID.
Start and warm-up the engine to normal operating temperature.
Is the 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 the idle speed.
Is the idle speed correct?
Yes
Go to the next step.
No
Repair or replace malfunctioning part according to idle speed inspection results.
4
Inspect the cooling fan control system operation.
Does the cooling fan control operate properly?
Yes
Go to the next step.
No
Repair or replace malfunctioning parts according to the cooling fan control system operation inspection results.
5
Connect the WDS or equivalent to the DLC-2. Access the following PID.
• APP
Verify that the PID value when the accelerator pedal is depressed and/or released.
Is the PID value normal?
Yes
Go to the next step.
No
Inspect and repair or replace the following parts:
• Accelerator pedal position sensor
6
Inspect the clutch pedal position switch.
Is the clutch pedal position switch normal?
Yes
Go to the next step.
No
Replace the clutch pedal position switch.
7
Visually inspect CKP sensor and the teeth of the pulse wheel.
Are the CKP sensor and the teeth of the pulse wheel normal?
Yes
Go to the next step.
No
Replace malfunctioning parts.
8
Measure gap between the CKP sensor and the teeth of the pulse wheel.

Specification

1.5-2.5 mm {0.059-0.098 in}

Is the gap within specification?
Yes
Go to the next step.
No
Adjust the CKP sensor position.
9
Visually inspect the CMP sensor and the teeth of the pulse wheel.
Are the CMP sensor and the teeth of the pulse wheel normal?
Yes
Inspect the following PIDs:
• ECT
• IAT
• MAF
• RPM
If the PID value is not as specified, repair or replace malfunctioning parts.
If the PID value is normal, go to the next step.
No
Replace malfunctioning parts.
10
Inspect fuel metering valve.
Is the fuel metering valve normal?
Yes
Go to the next step.
No
Replace the fuel pump.
11
Remove thermostat and inspect the operation.
Is the thermostat normal?
Yes
Go to the next step.
No
Replace the thermostat.
12
Inspect fuel injector relief pressure.
Is the fuel injector relief pressure normal?
Yes
Remove and inspect the supply pump and common rail.
No
Replace the fuel injector.
13
Verify test results.
• If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZ-CD 1.6 (Y6)].)
• If the malfunction remains, inspect related Service Information and perform repair or diagnosis.
- If the vehicle is repaired, troubleshooting is completed.
- If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZ-CD 1.6 (Y6)].)