NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [MZR 2.0, MZR 2.5]

id0103e1801400

8

ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION
•  The engine speed fluctuates between specified idle speed and lower speed and engine shakes excessively.
•  The idle speed is too slow and the 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
•  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
•  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)
•  PCV valve malfunction
•  PCM malfunction
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. (See BEFORE SERVICE PRECAUTION [MZR 2.0, MZR 2.5].) (See AFTER SERVICE PRECAUTION [MZR 2.0, MZR 2.5].)
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
Symptom 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
Inspect 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 or 1G)
Are all items normal?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
Repeat Step 2.
3
Connect the M-MDS to the DLC-2.
Switch the ignition to ON (engine off).
Retrieve any DTCs.
(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)
Are any DTCs present?
Yes
Go to the appropriate DTC inspection.
(See DTC TABLE [MZR 2.0, MZR 2.5].)
No
Go to the next step.
4
Is the engine overheating?
Yes
Go to the symptom troubleshooting “NO.17 COOLING SYSTEM CONCERNS-OVERHEATING”.
(See NO.17 COOLING SYSTEM CONCERNS-OVERHEATING [MZR 2.0, MZR 2.5].)
No
Go to the next step.
5
Connect the M-MDS to the DLC-2.
Access the MAF PID using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)
Drive the vehicle while monitoring the PID.
Is the MAF PID value 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.
Repair or replace the malfunctioning part according to the inspection results.
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 the symptom troubleshooting “NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY”.
For other symptoms:
•  Inspect the following:
―  Refrigerant charging amount
―  Condenser fan operation
•  Repair or replace the malfunctioning part according to the inspection results.
7
Visually inspect the CKP sensor and teeth of the crankshaft pulley.
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
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 or replace the suspected wiring harness.
9
Inspect the spark plug condition.
(See SPARK PLUG INSPECTION [MZR 2.0, MZR 2.5].)
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 for a clogged fuel injector.
Repair or replace the malfunctioning part according to the inspection results.
No
Install the spark plugs on original cylinders, then go to the next step.
10
Perform the Electronic Throttle Control System Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 2.0, MZR 2.5].)
Does the electronic throttle control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
11
Inspect the fuel line pressure.
(See FUEL LINE PRESSURE INSPECTION [MZR 2.0, MZR 2.5].)
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 the fuel pump unit.
High:
•  Replace the fuel pump unit.
12
Visually inspect for fuel leakage at the fuel injector O-ring and fuel line.
Repair or replace the malfunctioning part according to the inspection results.
Is the fuel line pressure held after the ignition is off?
Yes
Go to the next step.
No
Inspect the fuel injector.
(See FUEL INJECTOR INSPECTION [MZR 2.0, MZR 2.5].)
•  If the fuel injector has a malfunction:
―  Replace the fuel injector.
•  If the fuel injector is normal:
―  Replace the fuel pump unit.
13
Connect the M-MDS to the DLC-2.
Start the engine and idle it.
Access the LONGFT1 PID using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)
Measure the LONGFT1 PID at idle.
Is the PID value between −14% and +14%?
Yes
Go to the next step.
No
Less than specification (too rich):
•  Inspect the EVAP control system.
•  Repair or replace the malfunctioning part according to the inspection results.
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.
―  If the system has a malfunction:
•  Repair or replace the malfunctioning part according to the inspection results.
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
Inspect the following:
•  Purge solenoid valve
•  Evaporative emission control system
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
15
Visually inspect the exhaust system parts.
Is there any deformed exhaust system parts?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
16
Visually inspect the CMP sensor and teeth of the camshaft.
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
17
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 [MZR 2.0, MZR 2.5].)
No
Go to the next step.
18
Perform the Variable Valve Timing Control System Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 2.0, MZR 2.5].)
Does the variable valve timing control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
19
Is the engine compression correct?
(See COMPRESSION INSPECTION [MZR 2.0, MZR 2.5].)
Yes
Go to the next step.
No
Inspect for causes.
20
Inspect the PCV valve.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Replace the PCV valve and oil separator as a single unit.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)
No
Inspect the valve timing.
Repair or replace the malfunctioning part according to the inspection results.
21
•  Verify the test results.
―  If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZR 2.0, MZR 2.5].)
―  If a malfunction remains, inspect the related Service Information perform repair or diagnosis.
•  If the vehicle repaired, troubleshooting is completed.
•  If the vehicle not repaired or additional diagnostic information not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)