No. 14 Poor Fuel Economy: Notes

POSSIBLE CAUSES DESCRIPTIONS

14	POOR FUEL ECONOMY
DESCRIPTION	Fuel economy is unsatisfactory.
POSSIBLE CAUSE	Contaminated air cleaner element Engine cooling system malfunction Weak spark Spark plug malfunction Poor fuel quality Erratic signal from CKP sensor Erratic or no signal from CMP sensor Fuel pressure sensor or related circuit malfunction ECT sensor or related circuit malfunction Manifold absolute pressure (MAP) sensor or related circuit malfunction Accelerator position sensor or related circuit malfunction MAF sensor or related circuit malfunction Contaminated MAF sensor IAT sensor No.1 or related circuit malfunction IAT sensor No.2 or related circuit malfunction VSS or related circuit malfunction Variable swirl system malfunction Improper coolant level Inadequate fuel pressure (high-pressure side) Injection timing is incorrect Fuel injector or related circuit malfunction High pressure fuel pump malfunction Fuel leakage Fuel line restriction Fuel filter clogging PCV valve malfunction Brake dragging Clutch slippage A/C system improper operation Improper valve timing due to jumping out of timing chain Improper engine compression Turbocharger malfunction Charge air cooler malfunction Exhaust system and/or three-way catalytic converter clogging EGR system malfunction Vacuum leakage Injector driver module or related circuit 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 injury or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual. (See BEFORE REPAIR PROCEDURE ). (See AFTER REPAIR PROCEDURE ). CAUTION: Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

POOR FUEL ECONOMY

DESCRIPTION

Fuel economy is unsatisfactory.

POSSIBLE CAUSE

Contaminated air cleaner element
Engine cooling system malfunction
Weak spark
Spark plug malfunction
Poor fuel quality
Erratic signal from CKP sensor
Erratic or no signal from CMP sensor
Fuel pressure sensor or related circuit malfunction
ECT sensor or related circuit malfunction
Manifold absolute pressure (MAP) sensor or related circuit malfunction
Accelerator position sensor or related circuit malfunction
MAF sensor or related circuit malfunction
Contaminated MAF sensor
IAT sensor No.1 or related circuit malfunction
IAT sensor No.2 or related circuit malfunction
VSS or related circuit malfunction
Variable swirl system malfunction
Improper coolant level
Inadequate fuel pressure (high-pressure side)
Injection timing is incorrect
Fuel injector or related circuit malfunction
High pressure fuel pump malfunction
Fuel leakage
Fuel line restriction
Fuel filter clogging
PCV valve malfunction
Brake dragging
Clutch slippage
A/C system improper operation
Improper valve timing due to jumping out of timing chain
Improper engine compression
Turbocharger malfunction
Charge air cooler malfunction
Exhaust system and/or three-way catalytic converter clogging
EGR system malfunction
Vacuum leakage
Injector driver module or related circuit 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 injury or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.
  (See BEFORE REPAIR PROCEDURE ).
  
  (See AFTER REPAIR PROCEDURE ).
CAUTION:
- Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.