NO.7 ENGINE RUNS ROUGH/ROLLING IDLE [WLT-1, WLT-2]

id010396912700

7
Engine runs rough/rolling idle
DESCRIPTION
•  The engine speed fluctuates between the specified idle speed and a lower speed, and the engine shakes excessively.
•  The idle speed is too slow and the engine shakes excessively.
POSSIBLE CAUSE
•  Poor fuel quality
•  Air leakage from intake-air system
•  Intake-air system restriction
•  Incorrect idle speed
•  Engine overheating
•  A/C system improper operation
•  Glow system malfunction
•  Fuel leakage
•  Fuel filter clogging
•  Fuel line restriction
•  Incorrect fuel injection timing
•  Injection pump malfunction
•  Injection nozzle malfunction
•  Low engine *compression
•  FICD malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
•  Inspect for the following:
―  Proper fuel quality including water contamination
―  Loose bands on intake-air system
―  Cracks on intake-air system parts
―  Intake-air system restriction
•  Are all items normal?
Yes
Go to the next step.
No
Service if necessary.
Repeat Step 1.
2
•  Is the engine overheating?
Yes
Go to symptom troubleshooting "NO.13 COOLING SYSTEM CONCERNS-OVERHEATING."
No
Go to the next step.
3
•  Does the engine run normally after warm-up?
Yes
Go to the next step.
No
Go to step 6.
4
•  Inspect the glow plug and glow plug relay.
•  Is the glow system operation normal?
Yes
Go to step 7.
No
Repair or replace any malfunctioning part according to the glow system operation results.
5
Note
•  The following test should be performed on vehicles with the A/C system. If the following test cannot be performed due to engine stalls, go to the next step.
•  Go to the next step for vehicle without the A/C system.
•  Connect the pressure gauge to the A/C lines.
•  Turn the blower switch on.
•  Is the pressure within the specification?
Yes
Go to the next step.
No
A/C is always on:
•  Go to the symptom troubleshooting “NO 19. A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY.”
For other symptoms:
•  Inspect the following:
―  Refrigerant charging amount
―  Cooling fan operation
6
•  Inspect for FICD system operation.
•  Is the FICD operation normal?
Yes
Go to the next step.
No
Inspect the following:
•  Engine coolant temperature
•  Vacuum pump
•  Vacuum leaks around vacuum pump or fittings
•  FICD solenoid valve
•  FICD actuator
•  PCM terminal J voltage
•  Open circuit between FICD solenoid valve No.1 connector terminal B and PCM connector terminal C
•  Open circuit between FICD solenoid valve No.2 connector terminal B and PCM connector terminal P
Repair or replace any defective part as necessary.
If the FICD system is normal, go to the next step.
7
•  Depress the accelerator pedal slightly.
•  Crank the engine.
•  Does the engine start now?
Yes
Inspect and adjust the idle speed.
(See ENGINE TUNE-UP [WLT-1, WLT-2].)
If the symptom still appears, go to the next step.
No
Go to the next step.
8
•  Inspect the fuel leakage from the fuel pipe.
•  Is any fuel leakage found on the fuel pipe?
Yes
Repair or replace if necessary.
No
Go to the next step.
9
Note
•  The following test should be preformed on vehicles with EGR system. Go to the next step for vehicles without EGR system.
Carry out EGR system inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [WLT-1, WLT-2].)
Is the EGR system normal?
Yes
Go to the next step.
No
Repair or replace if necessary.
10
•  Measure the engine compression.
•  Is the compression normal?
Yes
Go to Step 12.
No
Go to the next step.
11
•  Inspect the timing belt for the following:
―  Chipping of gear teeth
―  Low tension
―  Breakage, damage or cracks
•  Is the timing belt normal?
Yes
Inspect for the following:
•  Burnt valve
•  Worn piston, piston ring or cylinder
•  Damaged cylinder head gasket
•  Damaged valve seat
•  Worn valve stem or valve guide
Repair or replace if necessary
No
If the timing is incorrect, adjust the timing.
If the timing belt is not normal, replace the timing belt.
12
•  Inspect the injection timing.
•  Is the injection timing normal?
Yes
Go to the next step.
No
Inspect the TCV.
(See TIMER CONTROL VALVE (TCV) INSPECTION [WLT-1, WLT-2].)
If the TCV is normal, adjust the injection timing.
13
•  Inspect the fuel filter for clogging.
•  Is the fuel filter normal?
Yes
Go to the next step.
No
Replace the fuel filter cartridge.
14
•  Inspect the fuel line for restriction.
•  Is any restriction found on the fuel line?
Yes
Repair or replace if necessary.
No
Go to the next step.
15
•  Remove the injection nozzle.
•  Inspect the injection nozzle for the following:
―  Clogged nozzle
―  Seized needle valve
―  Incorrect valve opening pressure
―  Malfunctioning nozzle gasket
•  Is the injection nozzle normal?
Yes
Go to the next step.
No
Repair or replace the injection nozzle.
16
•  Is the valve clearance correct?
Yes
Remove the FIP.
Inspect the FIP.
No
Adjust valve clearance.
17
•  Verify the test results. If normal, return to the diagnostic index to service any additional symptoms.