NO.14 POOR FUEL ECONOMY
14 POOR FUEL ECONOMY
DESCRIPTION
The fuel economy is unsatisfactory.
POSSIBLE
CAUSE
• Contaminated air cleaner element
• Air suction at intake-air system (between MAF sensor and intake ports)
• Poor fuel quality
• Inadequate fuel pressure
• Pressure regulator (integrated in fuel pump unit) malfunction
• Fuel pump relay stuck closed
• Fuel leakage from fuel injector
• Restriction in exhaust system
• Erratic signal from eccentric shaft position sensor
• Improper MAF sensor installation
• Improper fuel injector control operation (abnormal signals from MAF, ECT,
front/rear HO2S and IAT sensors to PCM)
• Knock sensor malfunction (abnormal signal to PCM)
• Contaminated MAF sensor
• Improper engine compression
! Engine internal malfunction
! Abnormal engine oil condition (viscosity, deterioration)
! Low oil pressure
! Excessive fuel pressure
! Metering oil pump malfunction
• Leakage or clogging in oil pipe
• Leakage or clogging in oil nozzle
• Eccentric shaft bypass valve malfunction (stuck open)
• Improper cooling fan control system operation
• Thermostat malfunction (stuck open)
• Improper engine coolant level
• Improper ignition timing
• Weak spark
• Spark plug malfunction
• Brake dragging
• Low tire pressure
• Clutch slippage (MT)
• Improper ATF level (AT)
• Improper A/C operation (A/C cut-off control does not operate)
WARNING: The following troubleshooting flow chart contains fuel system diagnosis and
repair procedures. Read the 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 s
ills and leaka
e are dan
erous. Fuel can i
nite and cause serious in
uries
(w) RX8-Engine Troubleshooting
Page 103
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