No. 14 Poor Fuel Economy

14	POOR FUEL ECONOMY
DESCRIPTION	The fuel economy is unsatisfactory.
POSSIBLE CAUSE	Contaminated air cleaner element Variable intake air control malfunction Engine cooling system malfunction Improper ATF level (AT) Weak spark Poor fuel quality Erratic or no signal from CMP sensor Clutch slippage (MT) Improper variable valve timing control system operation Improper coolant level Inadequate fuel pressure Spark plug malfunction PCV valve malfunction Brake dragging Improper valve timing due to jumping out of timing belt Contaminated MAF sensor Improper engine compression Exhaust system clogging 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 ". CAUTION: Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean 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 for the following: Air cleaner element for contamination ATF level (AT) Fuel quality Coolant level Brake dragging Clutch slippage (MT) Are all items normal?	Yes	Go to the next step.
1		No	Service if necessary. Repeat Step 1.
2	Turn the ignition switch to the ON position (Engine off). Retrieve any DTCs. Are there any DTCs displayed?	Yes	Go to the appropriate DTC inspection. (See DTC TABLE ).
2		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.Drive the vehicle while monitoring the PID.(See PCM INSPECTION ).Is the PID within specification?	Yes	Go to the next step.
3		No	Inspect for coolant leakage, cooling fan and condenser fan operations or thermostat operation.
4	Perform the Spark Test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION ). Is the strong blue spark visible at each cylinder?	Yes	Go to the next step.
4		No	Repair or replace the malfunctioning part according to spark test result.
5	Install the fuel pressure gauge between the fuel pipe and the fuel distributor. Start the engine and idle it. Measure the fuel line pressure during idle. Is the fuel line pressure correct during idle? (See FUEL LINE PRESSURE INSPECTION ).	Yes	Go to the next step.
5		No	Low: Inspect the fuel pump relay and fuel pump circuit. 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 ).
6	Perform the Variable Valve Timing Control System Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION ). Does the variable valve timing control system function properly?	Yes	Go to the next step.
6		No	Repair or replace the malfunctioning part according to the inspection results.
7	Perform the Variable Intake air Control Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION ). Does the variable intake air control function properly?	Yes	Go to the next step.
7		No	Repair or replace the malfunctioning part according to the inspection results.
8	Visually inspect the exhaust system part. Is there any deformed exhaust system?	Yes	Repair or replace the malfunctioning part according to the inspection results.
8		No	Go to the next step.
9	Inspect for contaminated MAF sensor. Is there any contamination?	Yes	Go to the next step.
9		No	Inspect for cause.
10	Inspect the MAF sensor for contamination. Is there any contamination?	Yes	Replace the MAF/IAT sensor. (See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION ).
10		No	Go to the next step.
11	Is the engine compression correct? (See COMPRESSION INSPECTION ).	Yes	Go to the next step.
11		No	Inspect for cause.
12	Inspect the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION ). Is there any malfunction?	Yes	Replace the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION ).
12		No	Inspect the valve timing. (See VARIABLE VALVE TIMING ACTUATOR INSPECTION
13	Verify test results. If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX ). If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. If vehicle is repaired, troubleshooting completed. If vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION ).