NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [MZI-3.7]

id0103d2801400

8 | ENGINE RUNS ROUGH/ROLLING IDLE
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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 | • Idle learning of drive-by-wire control system is not completed. • Poor fuel quality • Air cleaner restriction • Vacuum leakage • Disconnected electrical connectors • Air leakage from intake-air system parts • No battery power supply to PCM • Open or short circuit in PCM ground circuit • PCM DTC is stored. • Engine overheating • MAF sensor or related circuit malfunction • A/C system operation is improper. • PSP switch or related circuit malfunction • Erratic signal from CKP sensor • Ignition system malfunction ― Ignition coil malfunction ― Ignition coil related circuit malfunction ― Spark plug malfunction • Fuel leakage from fuel injector • Fuel injector clogging • Improper operation of drive-by-wire control system • Inadequate fuel pressure ― Fuel pump mechanical malfunction ― Fuel line restriction or clogging ― Pressure regulator malfunction (built-in fuel pump unit) • Fuel leakage from fuel system • Purge solenoid valve malfunction • PCV valve malfunction • Erratic or no signal from CMP sensor • Improper variable valve timing control system operation • Low engine compression • Improper valve timing 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 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 [MZI-3.7].)(See AFTER SERVICE PRECAUTION [MZI-3.7].) Caution • Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

Diagnostic procedure

STEP | INSPECTION | RESULTS | ACTION
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1 | Warm up the engine. Idle the engine for 5 min. Is the symptom disappeared? | Yes | Symptom troubleshooting completed. (Cause of this symptom is that the idle learning of drive-by-wire 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 • Ignition wiring • Electrical connections • Fuses • Smooth operation of throttle valve • Vacuum air leakage • Air cleaner restriction • PCM ground circuit (1B, 1E, 1J) 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 | Turn the ignition switch to the ON position (Engine off). Retrieve any PCM DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) Are there any DTCs displayed? | Yes | DTC is displayed: • Go to the appropriate DTC inspection. (See DTC TABLE [MZI-3.7].)
No | No DTC is displayed: • 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 [MZI-3.7].)
No | Go to the next step.
5 | Caution • While performing this step, always operate the vehicle in a safe and lawful manner. • When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later. Access the PCM PID MAF using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) Drive the vehicle with monitoring the PID. Is the MAF PID within the specification? | Yes | Go to the next step.
No | Inspect for open or short circuit of MAF sensor and related wiring harness. Repair or replace the malfunctioning part according to the inspection results.
6 | Note • The following test is for stall concerns with the A/C on. If other symptoms exist, go to the next step. Connect the pressure gauges to A/C low and high pressure side lines. Turn the A/C on and measure low side and high side pressures. (See REFRIGERANT PRESSURE CHECK.) Are pressures within specifications? | 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”. (See NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [MZI-3.7].) For other symptoms: • Inspect the following: ― Refrigerant charging amount ― Condenser fan operation • Repair or replace the malfunctioning part according to the inspection results.
7 | Note • The following test is for engine running rough with P/S on. If other symptoms exist, go to the next step. Start the engine and idle it. Access the PCM PID PSP using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) Is the PSP PID within the specification? | Yes | Go to the next step.
No | Inspect the PSP switch operation and wiring harness between the following: • PSP switch and PCM terminal 1G Repair or replace the malfunctioning part according to the inspection results.
8 | Inspect the CKP sensor. (See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [MZI-3.7].) Is the CKP sensor normal? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
9 | Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) for all cylinders. Are wiring harness conditions normal? | Yes | Go to the next step.
No | Repair or replace suspected wiring harness and connector.
10 | Perform the spark test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) Is strong blue spark visible at each cylinder? | Yes | Go to the next step. • If symptoms occurs with the A/C on, go to Step 15.
No | Repair or replace the malfunctioning part according to the inspection results.
11 | Verify the spark plug conditions when the spark plug removed in Step 10. 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 fuel injector. Spark plug is grayish white: • Inspect the fuel injector for clogging. Repair or replace the malfunctioning part according to the inspection results.
No | Install the spark plugs on original cylinders. Go to the next step.
12 | Perform the drive-by-wire control system operation inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) Does the drive-by-wire control system function properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
13 | Install the fuel pressure gauge between fuel pipe and fuel distributor. Start the engine and run it at idle. Measure the fuel line pressure during idle. (See FUEL LINE PRESSURE INSPECTION [MZI-3.7].) Is the fuel line pressure correct during idle? | Yes | Go to the next step.
No | Zero or low: • Inspect the following: ― Fuel pump relay ― Fuel pump circuit ― Fuel line for clogging • If there is no malfunction, replace the fuel pump unit. (Fuel pump or pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].) High: • Replace the fuel pump unit. (Pressure regulator malfunction) (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].)
14 | Visually inspect for fuel leakage at fuel injector, O-ring, and fuel line. Is there any fuel leakage? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
15 | Start the engine and idle it. Access the PCM PIDs LONG FT1 and LONG FT2 using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) Measure the LONG FT1 and LONG FT2 PIDs at idle. Is the PID value normal? | Yes | Go to the next step.
No | Less than the specification (too rich): • Inspect the EVAP control system. Greater than the specification (too lean): • Inspect for air leakage at intake-air system components. Repair or replace the malfunctioning part according to the inspection results. • If the system is normal, go to the next step.
16 | Disconnect the vacuum hose between purge solenoid valve and intake manifold from purge solenoid side. Plug opening end of vacuum hose. Start the engine. Is the engine stall now eliminated? | Yes | Inspect the following: • If purge solenoid valve is stuck open. • EVAP control system Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
17 | Note • The PCV valve cannot be reassembled once it is removed because the tabs will have bee n broken. Inspect the PCV valve without removing it from the vehicle. Inspect the PCV valve with it installed. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [MZI-3.7].) Is the PCV valve normal? | Yes | Go to the next step.
No | Replace the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [MZI-3.7].)
18 | Visually inspect the exhaust system part. Is there any deformed exhaust system part? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
19 | Inspect the CMP sensor. (See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [MZI-3.7].) Is the CMP sensor normal? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
20 | Inspect the variable valve timing control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) Does the variable valve timing control function properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
21 | Is the engine compression correct? | Yes | Inspect the valve timing. Repair or replace the malfunctioning part according to the inspection results.
No | Inspect for cause. Repair or replace the malfunctioning part according to the inspection results.
22 | • Verify test results. ― If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZI-3.7].) ― If malfunction remains, inspect related Service Information and perform repair or diagnosis. • If vehicle is repaired, troubleshooting completed. • If vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZI-3.7].)