NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [L8, LF, L5]

id010346801400

8

ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION
•  Engine speed fluctuates between specified idle speed and lower speed, and engine shakes excessively.
•  Idle speed is too slow and engine shakes excessively.
POSSIBLE CAUSE
•  Air leakage from intake air system parts
•  A/C system operation is improper
•  Erratic signal to ignition coil
•  Spark plug malfunction
•  Purge solenoid valve malfunction
•  Improper operation of electronic throttle control system
•  Idle learning of electronic throttle control system is not completed
•  EGR valve malfunction
•  Erratic or no signal from CMP sensor
•  Low engine compression
•  Improper valve timing
•  Improper variable valve timing control system operation (LF, L5)
•  Erratic signal from CKP sensor
•  Improper air/fuel mixture ratio control operation (abnormal signal form MAF sensor or A/F sensor, HO2S)
•  Open or short circuit in PCM ground circuit
•  Poor fuel quality
•  PCV valve malfunction
•  Air cleaner restriction
•  Restriction in exhaust system
•  Disconnected electrical connectors
•  Inadequate fuel pressure
•  Fuel pump body mechanical malfunction
•  Improper load signal input
•  Fuel line restriction or clogging
•  Improper fuel injection control operation
•  Fuel leakage from fuel injector
•  Fuel injector clogging
•  Engine overheating
•  Vacuum leakage
•  Pressure regulator malfunction (built-in fuel pump unit)
Warning
The following troubleshooting flow chart contains 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 injuries 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.
Caution
•  Disconnecting/connecting the quick release connector without cleaning it may cause damage to the fuel pipe and the 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
Warm up the engine.
Idle the engine for 5 min.
Does the symptom disappear?
Yes
Troubleshooting is completed. (Cause of this symptom is that the idle learning for electronic throttle control system is not completed.)
No
Go to the next step.
2
Verify the following:
•  External fuel shut off or accessory (such as kill switch, alarm)
•  Fuel quality (such as proper octane, contamination, winter/summer blend)
•  No air leakage from intake air system
•  Proper sealing of intake manifold and components attached to intake manifold: EGR valve
•  Ignition wiring
•  Electrical connections
•  Fuses
•  Smooth operation of throttle valve
•  PCM ground circuit (1E, 1F, 1G or 1BE)
Are all items normal?
Yes
Go to the next step.
No
Service if necessary.
Repeat Step 2.
3
Connect the M-MDS to the DLC-2.
Switch the ignition to ON (Engine off).
Retrieve any DTCs.
Are there any DTCs displayed?
Yes
DTC is displayed:
Go to the appropriate DTC inspection.
(See DTC TABLE [L8, LF, L5].)
No
No DTC is displayed:
Go to the next step.
4
Is the engine overheating?
Yes
Go to symptom troubleshooting "No.17 Cooling system concerns - Overheating".
(See NO.17 COOLING SYSTEM CONCERNS-OVERHEATING [L8, LF, L5].)
No
Go to the next step.
5
Connect the M-MDS to the DLC-2.
Access MAF PID.
Drive vehicle while monitoring the PID. Is the MAF PID within the specification?
Yes
Go to the next step.
No
Inspect for an open or short circuit in the MAF sensor and related wiring harness.
6
Note
•  The following test is for engine running at rough idle with A/C on. If other symptoms exist, go to the next step.
Connect a pressure gauge to the A/C low and high pressure side lines.
Start the engine and idle it.
Turn the A/C switch on.
Measure the low side and high side pressures.
Are the pressures within the specifications?
(See REFRIGERANT PRESSURE CHECK.)
Yes
Go to the next step.
No
If the A/C is always on, go to symptom troubleshooting "No.24 A/C is always on or A/C compressor runs continuously".
(See NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [L8, LF, L5].)
For other symptoms, inspect the following:
•  Refrigerant charging amount
•  Condenser fan operation
7
Visually inspect the CKP sensor and teeth of the crankshaft pulley.
(See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [L8, LF, L5].)
Are the CKP sensor and teeth of the crankshaft pulley normal?
Yes
Go to the next step.
No
Replace the malfunctioning part.
8
Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) for all cylinders. Are the wiring harness conditions normal?
Yes
Go to the next step.
No
Repair the wiring harnesses.
9
Inspect the spark plug condition.
(See SPARK PLUG INSPECTION [L8, LF, L5].)
Is the spark plug wet, covered with carbon or grayish white?
Yes
Spark plug is wet or covered with carbon:
Inspect for fuel leakage from the injector.
Spark plug is grayish white:
Inspect the fuel injector for clogging.
No
Install the spark plugs on original cylinders.
Go to the next step.
10
Perform the electronic throttle control system operation inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].)
Does the electronic throttle control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the electronic throttle control system operation inspection results.
11
Inspect the fuel line pressure.
(See FUEL LINE PRESSURE INSPECTION [L8, LF, L5].)
Is the fuel line pressure correct?
Yes
Go to the next step.
No
Low:
Inspect the fuel line for clogging.
If there is no malfunction, replace fuel pump unit.
High:
Replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)
12
Visually inspect for fuel leakage at the fuel injector, O-ring, and fuel line.
Service if necessary.
Does the fuel line pressure hold after the ignition is off?
(See FUEL LINE PRESSURE INSPECTION [L8, LF, L5])
Yes
Go to the next step.
No
Inspect the fuel injector.
(See FUEL INJECTOR INSPECTION [L8, LF, L5].)
If the fuel injector is normal, replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)
13
Connect the M-MDS to the DLC-2.
Start the engine and idle it.
Access the LONG FT1 PID.
Measure the LONG FT1 PID at idle.
Is the PID value between -14% and +14%?
Yes
Go to the next step.
No
LONG FT1 PID is out of specification.
Less than specification (too rich):
•  Inspect the EVAP control system.
Greater than specification (too lean):
•  Inspect for air leakage at the intake air system components.
―  If the system is normal, go to the next step.
14
Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from the purge solenoid valve side.
Plug the open end of the vacuum hose.
Start the engine.
Does the engine condition improve?
Yes
Check if the purge solenoid valve is stuck open mechanically.
Inspect the EVAP control system.
No
Go to the next step.
15
Remove and shake the PCV valve.
Does the PCV valve rattle?
Yes
Go to the next step.
No
Replace the PCV valve.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [L8, LF, L5].)
16
Visually inspect the exhaust system parts.
(See EXHAUST SYSTEM INSPECTION [L8, LF, L5].)
Is there any deformed exhaust system parts?
Yes
Replace the suspected part.
No
Go to the next step.
17
Visually inspect the CMP sensor and teeth of the camshaft.
(See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [L8, LF, L5].)
Are the CMP sensor and teeth of the camshaft normal?
Yes
Go to the next step.
No
Replace the malfunctioning part.
18
Inspect the engine condition while tapping the EGR valve housing.
Does the engine condition improve?
Yes
Replace the EGR valve.
(See EGR VALVE REMOVAL/INSTALLATION [L8, LF, L5].)
No
Go to the next step. (LF, L5)
Go to Step 20. (L8)
19
Inspect the variable valve timing control system operation.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].)
Does variable valve timing control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part.
20
Is the engine compression correct?
(See COMPRESSION INSPECTION [L8, LF, L5].)
Yes
Inspect the valve timing.
No
Inspect for causes.
21
•  Verify test results.
―  If normal, return to the diagnostic index to service any additional symptoms.
―  If the malfunction remains, inspect the 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.