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

id0103a0801400

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 | • Electrical connector disconnection • Poor fuel quality • Fuse malfunction • Air leakage from intake-air system • PCM ground circuit malfunction • Throttle valve malfunction • Engine overheating • MAF sensor and related wiring harness malfunction • Improper operation of A/C system • PSP switch and related wiring harness malfunction • No signal from CKP sensor due to sensor, related wire or wrong installation • Ignition coil related wiring harness malfunction • Spark plug malfunction • Improper operation of electronic throttle control system • Fuel supply system malfunction ― Fuel pump and fuel pump relay related circuit malfunction ― Fuel line clogging ― Fuel pump unit malfunction ― Fuel injector malfunction • A/F sensor malfunction ― Exhaust gas leakage between exhaust manifold and A/F sensor ― Loose installation of A/F sensor ― A/F sensor malfunction • Purge solenoid valve malfunction • EVAP control system malfunction • Restriction in exhaust system • Erratic signal from CMP sensor • EGR valve malfunction • Improper operation of variable valve timing control system • Low engine compression • PCV valve malfunction • Improper valve timing • PCM malfunction Warning The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read 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 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 [L8, LF].) (See AFTER SERVICE PRECAUTION [L8, LF].) Caution • Disconnecting/connecting quick release connector without cleaning it may possibly 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
--- | --- | --- | ---
1 | Warm up the engine and idle for 5 min. Is the symptom disappeared? | Yes | Symptom troubleshooting completed. (Cause of this symptom is that the idle learning of IAC system is not completed.)
No | Go to the next step.
2 | Verify the following: • Electrical connections • External fuel shut off or accessory (such as kill switch, alarm) • Fuel quality (such as proper octane, contamination, winter/summer blend) • Fuses • Ignition wiring • No air leakage from intake-air system • PCM ground circuit (PCM terminal 1AZ, 1BB, 1BD and/or 1BH) • Proper sealing of intake manifold and components attached to intake manifold: EGR valve • Smooth operation of throttle valve Is there any malfunction? | Yes | Repair or replace the malfunctioning part according to the inspection results. Repeat Step 2.
No | Go to the next step.
3 | Connect the M-MDS to the DLC-2. Perform the KOEO/KOER self test and DTC Reading Procedure. (See KOEO/KOER SELF TEST [L8, LF].) (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) Are any DTCs present? | Yes | Go to the appropriate DTC inspection. (See DTC TABLE [L8, LF].)
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 [L8, LF].)
No | Go to the next step.
5 | Connect the M-MDS to the DLC-2. Perform the PID/DATA Monitor and Record Procedure. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) Access the MAF PID. Drive vehicle with monitoring PID. Is MAF PID within specification? (See PCM INSPECTION [L8, LF].) | Yes | Go to the next step.
No | Inspect for open or short circuit of MAF sensor and related wiring harness. (See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR INSPECTION [L8, LF].) Repair or replace the malfunctioning part according to the inspection results.
6 | Note • Following test is for engine running rough idle with A/C on concerns. If other symptoms exist, go to the next step. Connect the pressure gauge to A/C low and high pressure side lines. Start engine and run it at idle. Turn A/C switch on. Measure low side and high side pressures. Are pressures within specifications? (See REFRIGERANT PRESSURE CHECK.) | Yes | Go to the next step.
No | If 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 [L8, LF].) 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 • Following test is for engine running rough with P/S on. If other symptoms exist, go to the next step. Start engine and idle it. Perform the PID/DATA Monitor and Record Procedure. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) Access the PSP PID. Inspect if PSP PID is On while turning the steering wheel right to left. Is PSP PID normal? | Yes | Go to the next step.
No | Inspect for open or short circuit in wiring between PSP switch and PCM terminal 2T. If the circuit has a malfunction: • Repair or replace the suspected wiring harness. If there is no malfunction: • Inspect the PSP switch. (See POWER STEERING PRESSURE (PSP) SWITCH INSPECTION [L8, LF].) • Replace the PSP switch, if necessary.
8 | Visually inspect the CKP sensor and teeth of crankshaft pulley. Is there any malfunction? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
9 | Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) for all cylinders. Is there any malfunction? | Yes | Repair or replace the suspected wiring harness.
No | Go to the next step.
10 | Inspect spark plug condition. (See SPARK PLUG INSPECTION [L8, LF].) 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 injector. Spark plug is grayish white: • Inspect for clogged fuel injector. Repair or replace the malfunctioning part according to the inspection results.
No | Install spark plugs on original cylinders. Go to the next step.
11 | Perform the Electronic Throttle Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) 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.
12 | Install the fuel pressure gauge between fuel pipe and fuel distributor. Start the engine and run it at idle. Measure fuel line pressure at idle. Is fuel line pressure correct at idle? (See FUEL LINE PRESSURE INSPECTION [L8, LF].) | Yes | Go to the next step.
No | Zero or low: • Inspect the fuel pump and fuel pump relay related circuit. • Inspect for clogged fuel line. • If there is no malfunction: ― Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].) • If there is a malfunction: ― Repair or replace the malfunctioning part according to the inspection results. High: • Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].)
13 | Visually inspect for fuel leakage at fuel injector, O-ring, and fuel line. Does fuel line pressure hold after ignition switch is turned off? (See FUEL LINE PRESSURE INSPECTION [L8, LF].) | Yes | Go to the next step.
No | Inspect the fuel injector. (See FUEL INJECTOR INSPECTION [L8, LF].) If the fuel injector is normal: • Replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].) If the fuel injector has a malfunction: • Replace fuel injector. (See FUEL INJECTOR REMOVAL/INSTALLATION [L8, LF].)
14 | Inspect the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR INSPECTION [L8, LF].) Is there any malfunction? | Yes | Inspect the followings: • Exhaust gas leakage between exhaust manifold and A/F sensor • Loose installation of A/F sensor If there is no malfunction: • Replace the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].) If there is a malfunction: • Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
15 | Disconnect the vacuum hose between purge solenoid valve and intake manifold from purge solenoid valve side. Plug opening end of vacuum hose. Start the engine. Does the engine condition improve? | Yes | Inspect if the purge solenoid valve is stuck open. (See PURGE SOLENOID VALVE INSPECTION [L8, LF].) Inspect the EVAP control system. Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
16 | 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.
17 | Visually inspect the CMP sensor and teeth of camshaft. Is there any malfunction? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
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].)
No | Go to the next step.
19 | Perform the Variable Valve Timing Control System Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Does the variable valve timing control system operate properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
20 | Perform the “COMPRESSION INSPECTION”. (See COMPRESSION INSPECTION [L8, LF].) Is the engine compression correct? | Yes | Go to the next step.
No | Inspect for cause.
21 | Inspect the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [L8, LF].) Is there any malfunction? | Yes | Replace the PCV valve.
No | Inspect the valve timing.
22 | Verify test results. • If normal, return to diagnostic index to service any additional symptoms. (See ENGINE SYMPTOM TROUBLESHOOTING [L8, LF].) • If malfunction remains, inspect related Service information perform repair or diagnosis. ― If vehicle repaired, troubleshooting completed. ― If vehicle not repaired or additional diagnostic information not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [L8, LF].)