NO.7 SLOW RETURN TO IDLE [L3 Turbo]SM2444507
NO.7 SLOW RETURN TO IDLE [L3 Turbo]

id0103b4801300

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
• ECT sensor or related circuit malfunction
• Thermostat is stuck open
• Fuel injection timing is incorrect
• Erratic signal from CKP sensor
• Erratic signal from CMP sensor
• APP sensor or related circuit malfunction
• Air suction in intake-air system
• MAF sensor or related circuit malfunction
• Fuel pressure sensor or related circuit malfunction
• Excessive fuel pressure
• Relief valve malfunction (built-in delivery pipe)
• Fuel injector malfunction
• Cooling fan control system malfunction
• Improper load signal input
• Injector driver circuit (built-in PCM) 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 [L3 Turbo].) (See AFTER SERVICE PRECAUTION [L3 Turbo].)
Caution
• Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION
1
Inspect the air suction in the intake-air system components while racing the engine to higher speed.
Is there any air suction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
2
Turn the ignition switch to the ON position.
Retrieve any DTCs using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [L3 Turbo].)
No
Go to the next step.
3
Access the ECT PID using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
Start and warm-up the engine to normal operating temperature.
Is the ECT PID value below 82 °C {180 °F}?
Yes
Go to the next step.
No
Perform the symptom troubleshooting “NO.18 COOLING SYSTEM CONCERNS-RUNS COLD”.
(See NO.18 COOLING SYSTEM CONCERNS-RUNS COLD [L3 Turbo].)
4
Verify the cooling fan operation.
Does the cooling fan operate properly according to the ECT PID value?
Yes
Go to the next step.
No
Perform the Cooling Fan Control System Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L3 Turbo].)
If there is any malfunction:
Repair or replace the malfunctioning part according to the inspection results.
5
Inspect the CMP and CKP sensor for the following:
• Installation condition (See CAMSHAFT POSITION (CMP) SENSOR REMOVAL/INSTALLATION [L3 Turbo].) (See CRANKSHAFT POSITION (CKP) SENSOR REMOVAL/INSTALLATION [L3 Turbo].)
• Damaged trigger wheel and camshaft
• Open or short circuit in the wiring harnesses
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
6
Access the following PIDs using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
• ECT
• APP1
• APP2
• MAF
• PSP (PCM terminal 1AD)
Do the PIDs indicate the correct values under trouble condition?
(See PCM INSPECTION [L3 Turbo].)
Yes
Go to the next step.
No
Inspect the suspected parts and related wiring harness.
• If normal:
― Perform the “INTERMITTENT CONCERN TROUBLESHOOTING” procedure. (See INTERMITTENT CONCERN TROUBLESHOOTING [L3 Turbo].)
• If not:
― Repair or replace the malfunctioning part according to the inspection results.
7
Access the FUEL_PRES PID using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
Is the FUEL_PRES PID value within the specification?
(See PCM INSPECTION [L3 Turbo].)
Yes
Go to Step 11.
No
Go to the next step.
8
Is the vehicle accelerate performance normally?
Yes
Go to the next step.
No
Go to Step 10.
9
Inspect the fuel pressure sensor.
(See FUEL PRESSURE SENSOR INSPECTION [L3 Turbo].)
Is there any malfunction?
Yes
Replace the fuel delivery pipe.
(See FUEL INJECTOR REMOVAL/INSTALLATION [L3 Turbo].)
No
Go to Step 11.
10
Replace the high pressure fuel pump.
(See HIGH PRESSURE FUEL PUMP REMOVAL/INSTALLATION [L3 Turbo].)
Access the FUEL_PRES PID using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
Is the FUEL_PRES PID value within the specification?
(See PCM INSPECTION [L3 Turbo].)
Yes
High pressure fuel pump or spill valve control solenoid valve (built-in high pressure fuel pump) malfunction.
• Go to Step 13.
No
Relief valve malfunction.
• Replace the fuel delivery pipe. (See FUEL INJECTOR REMOVAL/INSTALLATION [L3 Turbo].)
11
Perform the Fuel Injector Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L3 Turbo].)
Do the fuel injectors operate normally?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
12
Remove the thermostat and inspection operation.
(See THERMOSTAT REMOVAL/INSTALLATION [L3 Turbo].)
(See THERMOSTAT INSPECTION [L3 Turbo].)
Is there any malfunction?
Yes
Replace the thermostat.
(See THERMOSTAT REMOVAL/INSTALLATION [L3 Turbo].)
No
Inspect the throttle body.
(See THROTTLE BODY INSPECTION [L3 Turbo].)
Repair or replace the malfunctioning part according to the inspection results.
• If the throttle body is normal or the problem remains:
― Replace the PCM (injector driver circuit malfunction). (See PCM REMOVAL/INSTALLATION [L3 Turbo].)
13
Verify test results.
• If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [L3 Turbo].)
• If the malfunction remains, inspect the related Service Information and perform the repair or diagnosis.
― If the vehicle is repaired, troubleshooting is completed.
― If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.