NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [WITH WU-TWC]


8	ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION	• The engine speed fluctuates between the specified idle speed and lower speed and the 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 • IAC valve improper operation • EGR valve malfunction (ZJ) • 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 • 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 • Steering angle sensor or related circuit 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 injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete the "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual. Caution • If there is foreign material on the connecting area of the quick release connector, it might damage the connector or the fuel pipe. To prevent this, disconnect the connector and clean the connecting area before connecting.


STEP	INSPECTION	RESULTS	ACTION
1	Inspect the following: • External fuel shut off or accessory (kill switch, alarm etc.) • Fuel quality (e.g. proper octane, contamination, winter/summer blend) • No air leakage from the intake-air system • Proper sealing of the intake manifold and components attached to the intake manifold: IAC valve, EGR valve (ZJ) • Ignition wiring • Electrical connections • Fuses • Smooth operation of the throttle valve Are all items normal?	Yes	Go to the next step.
1		No	Service if necessary. Repeat Step 1.
2	Connect the WDS or equivalent to DLC-2. Retrieve any continuous memory, KOEO and KOER DTCs. (See KOEO/KOER SELF-TEST.) Are any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC test.
2		No	No DTC is displayed: Go to the next step.
3	Is the engine overheating?	Yes	Go to symptom troubleshooting "No.17 Cooling system concerns - Overheating".
3	Is the engine overheating?	No	Go to the next step.
4	Note • The following test is for concerns with engines running at rough idle with the 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 specifications?	Yes	Go to the next step.
4		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". For other symptoms, inspect the following: • Refrigerant charging amount • Condenser fan operation
5	Note • The following test is for concerns with engines running at rough with the P/S on. If other symptoms exist, go to the next step. Start the engine and idle it. Access the PSP PID. Inspect if the PSP PID is on while turning the steering wheel right to left. Is the PSP PID normal?	Yes	Inspect the PSP switch operation and the wiring harness between the PSP switch connector and the PCM connector terminal 2AC.
5		No	Go to the next step.
6	Visually inspect the CKP sensor and the teeth of the crankshaft pulley. Are the CKP sensor and the teeth of the crankshaft pulley normal?	Yes	Go to the next step.
6		No	Replace the malfunctioning parts.
7	Measure the gap between the CKP sensor and the teeth of crankshaft pulley. Specification 0.5-1.5 mm {0.02-0.05 in} Is the gap within specification?	Yes	Go to the next step.
7		No	Replace the plate.
8	Inspect the ignition coil related harness condition (intermittent open or short) for all cylinders. Are the harness conditions normal?	Yes	Go to the next step.
8		No	Repair the suspected wiring harnesses.
9	Inspect the spark plugs. 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 for clogged fuel injector.
9		No	Install the spark plugs on the original cylinders. Go to the next step.
10	Start the engine and disconnect the IAC valve connector. Does the rpm drop or the engine stall?	Yes	Go to the next step.
10		No	Inspect the IAC valve and the wiring harness.
11	Install a fuel pressure gauge between the fuel pipe and the fuel distributor. Start the engine and idle it. Measure the fuel line pressure at idle. Is the fuel line pressure correct at idle?	Yes	Go to the next step.
11		No	Zero or low: Inspect for fuel leakage inside the pressure regulator. Inspect for a clogged main fuel line. High: Inspect the pressure regulator for the cause of high pressure. Inspect for a clogged fuel return line. Inspect the vacuum hose to the pressure regulator.
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 switch is turned off?	Yes	Go to the next step.
12		No	Inspect the pressure regulator diaphragm. • If the condition is normal, inspect the fuel injector. • If the condition is not normal, replace the pressure regulator.
13	Connect the WDS or equivalent to the DLC-2. Note • With the ignition switch off, the SWA PID value is cleared to the initial value (300 °). If the SWA PID does not move from 300 °, drive the vehicle above 20km/h {12 mph} to set the steering angle sensor straight ahead position. Start the engine and idle it, then drive the vehicle straight at over 20 km/h {12 mph}. Access and monitor SWA PID. Is SWA PID normal?	Yes	Go to the next step.
13		No	Inspect and repair or replace steering angle sensor and related circuit.
14	Connect the WDS or equivalent to the DLC-2. Start the engine and idle it. Access the O2S11 PID. Is the O2S11 PID normal? • More than 0.45 V when accelerator pedal is suddenly depressed: rich condition • Less than 0.45 V during fuel cut: lean condition	Yes	Go to the next step.
14		No	Inspect, repair or replace the malfunctioning HO2S, wiring harness, connector or terminal, then go to the next step.
15	Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from the 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 sticks open mechanically. Inspect the EVAP control system.
15		No	Go to the next step.
16	Remove and shake the PCV valve. Does the PCV valve rattle?	Yes	Go to the next step.
16	Remove and shake the PCV valve. Does the PCV valve rattle?	No	Replace the PCV valve.
17	Visually inspect the exhaust system part. Is there any deformed exhaust system part?	Yes	Replace the suspected part.
17		No	Go to the next step.
18	Visually inspect the CMP sensor and teeth of camshaft pulley. Are the CMP sensor and teeth of the camshaft pulley normal?	Yes	Go to the next step. (with EGR system) Go to Step 20. (without EGR system)
18		No	Replace the malfunctioning parts.
19	Inspect the engine condition while tapping the EGR valve housing. Does the engine condition improve?	Yes	Replace the EGR valve.
19		No	Go to the next step.
20	Inspect variable valve timing control system operation. Does the variable valve timing control system function properly?	Yes	Go to the next step.
20		No	Repair or replace the malfunctioning parts.
21	Is the engine compression correct?	Yes	With EGR system: Remove the EGR valve and visually inspect for mechanically stuck EGR valve. • If there is no malfunction, inspect valve timing. Without EGR system: Inspect the valve timing.
21	Is the engine compression correct?	No	Inspect for the cause.
22	Verify the test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, inspect related Service information and perform repair or diagnosis. - If the vehicle is repaired, the troubleshooting is completed. - If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM.