14 Poor Fuel Economy [Lf] - Mazda 3 Workshop Manual

Mazda 3 Workshop Manual – Engine + Wiring Diagrams + Diagnostic Trouble Codes
Install fuel pressure gauge between the fuel
pipe and fuel distributor.
Start the engine and idle it.
5 Measure fuel line pressure during idle.
Is fuel line pressure correct during idle?
(See FUEL LINE PRESSURE
INSPECTION.)
Verify test results.
• If normal, return to diagnostic index to service any additional symptoms.
(See ENGINE SYMPTOM TROUBLESHOOTING
• If malfunction remains, inspect related Service information perform repair or diagnosis.
6
- If vehicle repaired, troubleshooting completed.
- If vehicle not repaired or additional diagnostic information not available, replace the
PCM.
(See PCM REMOVAL/INSTALLATION
NO.14 POOR FUEL ECONOMY [LF]
14
DESCRIPTION Fuel economy is unsatisfactory.
• Contaminated air cleaner element
• Variable intake-air control malfunction
• Engine cooling system malfunction
• Weak spark
• Poor fuel quality
POSSIBLE
• Erratic or no signal from CMP sensor
CAUSE
• Clutch slippage
• Variable tumble control malfunction
• Improper coolant level
• Inadequate fuel pressure
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POOR FUEL ECONOMY
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Inspect ignition timing.
Low:
Inspect the fuel line for clogging.
• If there is no malfunction, replace the
fuel pump unit.
(See FUEL PUMP UNIT
REMOVAL/INSTALLATION.)
High:
Replace the fuel pump unit.
(See FUEL PUMP UNIT
REMOVAL/INSTALLATION.)
[LF].)
[LF].)
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