NO.14 POOR FUEL ECONOMY [MZR 1.8, MZR 2.0, MZR 2.5]

id0103d4802000

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
•  Low tire pressure
•  PCM DTC is stored
•  Engine cooling system malfunction
•  Spark plug malfunction
•  Excessive or insufficient fuel pressure
―  Fuel pump relay or fuel pump circuit malfunction
―  Clogging fuel line
―  Pressure regulator malfunction (built-in fuel pump unit)
―  Fuel pump unit malfunction
•  Improper operation of variable tumble control
•  Improper operation of variable valve timing control system (MZR 2.0, MZR 2.5)
•  Improper operation of variable valve intake air control (MZR 2.0, MZR 2.5)
•  Exhaust system clogging
•  Contaminated MAF sensor
•  Low engine compression
•  Improper valve timing
•  PCV valve malfunction
Warning
•  The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before servicing the fuel system:
―  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 [MZR 1.8, MZR 2.0, MZR 2.5].) (See AFTER SERVICE PRECAUTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Caution
•  Disconnecting/connecting the quick release connector without cleaning it may 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:
•  Air cleaner element for contamination
•  ATF level (ATX)
•  Brake dragging
•  Clutch slippage (MTX)
•  Coolant level
•  Fuel quality
•  Tire pressure
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
Perform the PCM DTC inspection using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [MZR 1.8, MZR 2.0, MZR 2.5].)
Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [MZR 1.8, MZR 2.0, MZR 2.5].)
No
Go to the next step.
3
Caution
•  While performing this step, always operate the vehicle in a safe and lawful manner.
•  When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later.
Access the ECT PID using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [MZR 1.8, MZR 2.0, MZR 2.5].)
Drive the vehicle while monitoring the ECT PID.
Is the ECT PID value within the specification?
(See PCM INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Yes
Go to the next step.
No
Inspect the following:
•  Coolant leakage
•  Cooling fan and condenser fan operation
•  Thermostat operation
Repair or replace the malfunctioning part according to the inspection results.
4
Perform the Spark Test.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is a 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.
Repeat Step 1.
5
Inspect the fuel line pressure.
(See FUEL LINE PRESSURE INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Zero or low:
•  Inspect the fuel pump relay and the fuel pump circuit.
•  Inspect the fuel line for clogging.
―  If there is any malfunction:
•  Repair or replace the malfunctioning part according to the inspection results.
―  If there is no malfunction:
•  Replace the fuel pump unit.
High:
•  Replace the fuel pump unit.
No
Go to the next step.
6
Perform the Variable Tumble Control Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
MZR 1.8:
•  Go to Step 9.
MZR 2.0, MZR 2.5:
•  Go to the next step.
7
Perform the Variable Valve Timing Control System Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
8
Perform the Variable Intake Air Control Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
9
Visually inspect the exhaust system parts.
Are there any deformed exhaust system parts?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
10
Inspect the MAF sensor for contamination.
Is there any contamination?
Yes
Replace the MAF/IAT sensor.
(See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [MZR 1.8, MZR 2.0, MZR 2.5].)
No
Go to the next step.
11
Inspect the engine compression.
(See COMPRESSION INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
No
Go to the next step.
12
Inspect the PCV valve.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [MZR 1.8, MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Replace the PCV valve and the oil separator as a single unit, then go to the next step.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [MZR 1.8, MZR 2.0, MZR 2.5].)
No
Inspect the valve timing.
(See VARIABLE VALVE TIMING ACTUATOR INSPECTION [MZR 2.0, MZR 2.5].)
Repair or replace the malfunctioning part according to the inspection results.
13
Verify test results.
•  If normal, return to the diagnostic index to service any additional symptoms.
•  If the malfunction remains, inspect the related Service Information and perform the repair or diagnosis.
―  If the vehicle is repaired, troubleshooting is completed.
―  If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.