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

id0103e1802000

14

POOR FUEL ECONOMY
DESCRIPTION
•  Fuel economy is unsatisfactory.
POSSIBLE CAUSE
•  Contaminated air cleaner element
•  Variable intake air control malfunction
•  Engine cooling system malfunction
•  Improper ATF level (ATX)
•  Weak spark
•  Poor fuel quality
•  Erratic or no signal from CMP sensor
•  Clutch slippage (MTX)
•  Variable tumble control malfunction
•  Improper operation of variable valve timing control system
•  Improper coolant level
•  Inadequate fuel pressure
•  Spark plug malfunction
•  Brake dragging
•  Improper valve timing due to jumping out of timing chain
•  Contaminated MAF sensor
•  Improper engine compression
•  Exhaust system clogging
•  PCV valve malfunction
•  PCM malfunction
Warning
The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read following warnings before servicing 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 2.0, MZR 2.5].) (See AFTER SERVICE PRECAUTION [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)
•  Fuel quality
•  Coolant level
•  Brake dragging
•  Clutch slippage (MTX)
Are all items normal?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results.
Repeat Step 1.
2
Connect the M-MDS to the DLC-2.
Switch the ignition to ON (engine off).
Retrieve any DTCs.
(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)
Are any DTCs present?
Yes
Go to the appropriate DTC inspection.
(See DTC TABLE [MZR 2.0, MZR 2.5].)
No
Go to the next step.
3
Connect the M-MDS to the DLC-2.
Access the ECT PID using the M-MDS while driving the vehicle.
(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)
Is the PID value within specification?
(See PCM INSPECTION [MZR 2.0, MZR 2.5].)
Yes
Go to the next step.
No
Inspect for coolant leakage, and inspect the cooling fan and condenser fan operations or and inspect the 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 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.
5
Inspect the fuel line pressure.
(See FUEL LINE PRESSURE INSPECTION [MZR 2.0, MZR 2.5].)
Is the fuel line pressure correct?
Yes
Go to the next step.
No
Low:
•  Inspect the following:
―  Fuel pump relay and the fuel pump circuit
―  Fuel line for clogging
•  If there is a 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.
6
Perform the Variable Tumble Control Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 2.0, MZR 2.5].)
Is the variable tumble control normal?
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 [MZR 2.0, MZR 2.5].)
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
Perform the Variable Intake air Control Operation Inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZR 2.0, MZR 2.5].)
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 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
Remove the contamination and clean the MAF sensor.
•  If excessive amount of contamination:
―  Replace the MAF/IAT sensor.
No
Go to the next step.
11
Is the engine compression correct?
(See COMPRESSION INSPECTION [MZR 2.0, MZR 2.5].)
Yes
Go to the next step.
No
Inspect for cause.
12
Inspect the PCV valve.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [MZR 2.0, MZR 2.5].)
Is there any malfunction?
Yes
Replace the PCV valve and oil separator as a single unit.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)
No
Inspect the valve timing.
Repair or replace the malfunctioning part according to the inspection results.
13
•  Verify the test results.
―  If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZR 2.0, MZR 2.5].)
―  If a malfunction remains, inspect the related Service Information perform repair or diagnosis.
•  If the vehicle repaired, troubleshooting is completed.
•  If the vehicle not repaired or additional diagnostic information not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)