NO.14 POOR FUEL ECONOMY [ZJ, ZY]

id0103b0802000

14

POOR FUEL ECONOMY
DESCRIPTION
•  Fuel economy is unsatisfactory.
POSSIBLE CAUSE
•  Contaminated air cleaner element
•  Improper ATF level (ATX)
•  Brake dragging
•  Clutch slippage (MTX)
•  Improper coolant level
•  Poor fuel quality
•  Continuous memory DTC is stored
•  Variable intake air control malfunction
•  Engine cooling system malfunction
•  Spark plug malfunction
•  Inadequate fuel pressure
•  Fuel pump unit malfunction
•  Improper operation of variable tumble control
•  Improper operation of variable valve timing control system
•  Improper operation of variable valve timing control system
•  Improper operation of variable intake air control system (if equipped)
•  Restriction in exhaust system
•  Contaminated MAF sensor
•  Improper engine compression
•  PCV valve malfunction
•  Valve timing malfunction
•  PCM 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 SERVICE PRECAUTION" and "AFTER SERVICE PRECAUTION" 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 fuel pipe. To prevent this, disconnect the connector and clean the connecting area before connecting.

Diagnostic procedure

STEP

INSPECTION

ACTION
1
Inspect the following:
•  Air cleaner element for contamination
•  ATF level
•  Brake dragging
•  Clutch slippage
•  Coolant level
•  Fuel quality
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
Repeat Step 1.
No
Go to the next step.
2
Connect the M-MDS to the DLC-2.
Perform the KOEO/KOER self test.
(See KOEO/KOER SELF TEST [ZJ, ZY].)
Are any continuous memory DTCs present?
Yes
Go to the appropriate DTC inspection.
(See DTC TABLE [ZJ, ZY].)
No
Go to the next step.
3
Connect the M-MDS to the DLC-2.
Perform the PID/DATA Monitor and Record Procedure and access the ECT PID.
(See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].)
Monitor the each PID while driving the vehicle.
Are the PIDs normal?
(See PCM INSPECTION [ZJ, ZY].)
Yes
Go to the next step.
No
Inspect for coolant leakage, cooling fan operations or thermostat operation.
Repair or replace the malfunctioning part according to the inspection results.
4
Perform the Spark Test.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)
Is the strong blue spark visible at each cylinder?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
5
Install the fuel pressure gauge between the fuel pipe and the fuel distributor.
Start the engine and idle it.
Measure the fuel line pressure during idle.
Is the fuel line pressure correct during idle?
(See FUEL LINE PRESSURE INSPECTION [ZJ, ZY].)
Yes
Go to the next step.
No
Low:
•  Inspect for clogged fuel line.
•  If normal:
―  Replace the fuel pump unit.
High:
•  Replace the fuel pump unit.
6
Perform the Variable Tumble Control Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)
Does the variable tumble control function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
7
Perform the Variable Valve Timing Control System Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)
Does the variable valve timing control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
8
Note
•  Following test is for the variable intake air control system. If not equipped, go to the next step.
Perform the Variable Intake Air Control Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)
Does the variable intake air control function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
9
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.
10
Inspect the MAF sensor for contaminated.
(See MASS AIR FLOW (MAF) SENSOR INSPECTION [ZJ, ZY].)
Is there any contamination?
Yes
Replace the MAF/IAT sensor.
(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)
No
Go to the next step.
11
Inspect the PCV valve operation.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [ZJ, ZY].)
Is there any malfunction?
Yes
Replace the PCV valve and the oil separator as a single unit.
(See PURGE SOLENOID VALVE REMOVAL/INSTALLATION [ZJ, ZY].)
No
Inspect the valve timing.
Repair or replace the malfunctioning part according to the inspection results.
12
Verify test results.
•  If normal, return to diagnostic index to service any additional symptoms.
•  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.