NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [LF, L3]

id0103008014b2

8

ENGINE RUNS ROUGH/ROLLING IDLE

DESCRIPTION

• Engine speed fluctuates between the specified idle speed and lower speed, and the engine shakes excessively.
• 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
• Spark leakage from high-tension leads
• Spark plug malfunction
• Purge solenoid valve malfunction
• IAC valve improper operation
• EGR valve malfunction (Unleaded gasoline model)
• Erratic or no signal from CMP sensor
• Low engine compression
• Improper valve timing
• Improper variable valve timing control system operation (L3)
• 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
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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.
(See BEFORE REPAIR PROCEDURE [LF, L3].)
(See AFTER REPAIR PROCEDURE [LF, L3].)
Caution
• Disconnecting/connecting the quick release connector without cleaning it may possibly 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
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 intake-air system
• Proper sealing of the intake manifold and components attached to the intake manifold: EGR valve (unleaded gasoline model), IAC valve
• Ignition wiring
• Electrical connections
• Fuses
• Smooth operation of throttle valve
Are all items normal?
Yes
Go to the next step.
No
Service if necessary.
Repeat Step 1.
2
Connect the WDS or equivalent to the DLC-2.
Retrieve any continuous memory, KOEO and KOER DTCs.
Are any DTCs displayed?
Yes

DTC is displayed:

Go to the appropriate DTC test.
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".
No
Go to the next step.
4
Note
• The following test is for engines idling roughly with the A/C on concerns. If other symptoms exist, go to the next step.
Connect pressure gauge to the A/C low and high pressure side lines.
Start the engine and run it at idle.
Turn the A/C switch on.
Measure the low side and high side pressures.
Are the pressures within the specifications?
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".
For other symptoms, inspect the following:
• Refrigerant charging amount
• Condenser fan operation
5
Note
• The following test is for engines running rough with the P/S on. If other symptoms exist, go to the next step.
Start the engine and run it at idle.
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 power steering pressure switch operation and the wiring harness between the P/S pressure switch connector and PCM connector terminal 1Z.
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.
No
Replace the malfunctioning parts.
7
Measure the gap between the CKP sensor and teeth of the crankshaft pulley.
Specification

0.5-1.5 mm {0.020-0.075 in}

Is the gap within specification?
Yes
Go to the next step.
No
Adjust the CKP sensor.
8
Inspect for cracks on the high-tension leads.
Are there any cracks on the high-tension leads?
Yes
Repair the suspected high-tension leads.
No
Go to the next step.
9
Inspect 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 the injector.

Spark plug is grayish white:

Inspect for clogged fuel injector.
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.
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 run it at idle.
Measure the fuel line pressure at idle.
Is the fuel line pressure correct at idle?
Yes
Go to the next step.
No

Zero or low:

Inspect for a clogged fuel line.
If normal, 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.
Service if necessary.
Does the fuel line pressure hold after the ignition switch is turned off?
Yes
Go to the next step. (Unleaded gasoline model)
Go to Step 14. (Leaded gasoline model)
No
Inspect the fuel injector.
If the fuel injector is normal, replace fuel pump unit.
13
Connect the WDS or equivalent to the DLC-2.
Start the engine and run it at idle.
Access the O2S11 PID.
Is the O2S11 PID normal?

• More than 0.45 V when the accelerator pedal is suddenly depressed: rich condition

• Less than 0.45 V during fuel cut: lean condition

Yes
Go to the next step.
No
Inspect and repair or replace the applicable HO2S, harness connector or terminal, then go to the next step.
14
Disconnect 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 if the purge solenoid valve sticks 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.
16
Inspect for a restriction in the exhaust system.
Is there any restriction?
Yes
Inspect the exhaust system.
No
Go to the next step.
17
Visually inspect the CMP sensor and the teeth of the camshaft.
Are the CMP sensor and the teeth of the camshaft normal?
Yes
Go to the next step. (Unleaded gasoline model)
Go to Step 19. (Leaded gasoline model)
No
Replace the malfunctioning parts.
18
Inspect the engine condition while tapping the EGR valve housing.
Does the engine condition improve?
Yes
Replace the EGR valve.
No
Go to the next step.
19
Note
• The following test should be performed for vehicles with the variable valve timing control system. Go to the next step for vehicles without the variable valve timing control system.
Inspect the variable valve timing control system operation.
Does the variable valve timing control system work properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
20
Is the engine compression correct?
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, replace the PCM.