NO.14 POOR FUEL ECONOMY [WITH WU-TWC]


14	POOR FUEL ECONOMY
DESCRIPTION	Fuel economy is unsatisfactory.
POSSIBLE CAUSE	• Contaminated air cleaner element • VIS malfunction (if equipped) • Engine cooling system malfunction • Improper ATF level (ATX) • Weak spark • Poor fuel quality • Erratic or no signal from CMP sensor • Clutch slippage (MTX) • VTCS malfunction • 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 the timing belt • Contaminated MAF sensor • Improper engine compression • Exhaust system clogging • Steering angle sensor 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 injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete the "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual. Caution • If there is foreign material on the connecting area of the quick release connector, it might damage the connector or the fuel pipe. To prevent this, disconnect the connector and clean the connecting area before connecting.


STEP	INSPECTION	RESULTS	ACTION
1	Inspect the following: • Air cleaner element for contamination • ATF level • Fuel quality • Coolant level • Brake dragging • Clutch slippage Are all items normal?	Yes	Go to the next step.
1		No	Service if necessary. Repeat Step 1.
2	Connect the WDS or equivalent to the DLC-2. Retrieve any continuous memory, KOEO and KOER DTCs. (See KOEO/KOER SELF-TEST.) Are there any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC test.
2		No	No DTC is displayed: Go to the next step.
3	Access ECT PID. Drive the vehicle while monitoring the PID. 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	Note • With the ignition switch off, the SWA PID value is cleared to the initial value (300 °). If the SWA PID does not move from 300 °, drive the vehicle above 20km/h {12 mph} to set the steering angle sensor to the straight ahead position. Start the engine and drive it above 20km/h {12 mph}. Access and monitor SWA PID. Is the SWA PID normal?	Yes	Go to the next step.
4		No	Inspect and repair or replace the steering angle sensor or related circuit.
5	Carry out a spark test. Is a strong blue spark visible at each cylinder?	Yes	Go to the next step.
5		No	Repair or replace the malfunctioning part according to spark test results.
6	Install a fuel pressure gauge between fuel pipe and the fuel distributor. Start the engine and idle it. Measure the fuel line pressure at idle. Is the fuel line pressure correct at idle?	Yes	Go to the next step.
6		No	Zero or low: Inspect the fuel pump relay and fuel pump related circuits. Inspect for fuel leakage inside pressure regulator. Inspect for a clogged main fuel line. High: Inspect the pressure regulator for the cause of high pressure. Inspect for clogged fuel return line. Inspect the vacuum hose to the pressure regulator.
7	Inspect the VTCS operation. Does the VTCS function properly?	Yes	Go to the next step.
7		No	Repair or replace the malfunctioning parts.
8	Inspect the variable valve timing control system operation. Does the variable valve timing control system work properly?	Yes	Go to the next step.
8		No	Repair or replace the malfunctioning parts.
9	Note • The following test should be performed for vehicles with the VIS. Go to the next step for vehicles without the VIS. Inspect the VIS operation. Does the VIS function properly?	Yes	Go to the next step.
9		No	Repair or replace the malfunctioning parts.
10	Remove and shake the PCV valve. Does the PCV valve rattle?	Yes	Go to the next step.
10	Remove and shake the PCV valve. Does the PCV valve rattle?	No	Replace the PCV valve.
11	Visually inspect the exhaust system part. Is there any deformed exhaust system part?	Yes	Replace the suspected part.
11		No	Go to the next step.
12	Inspect for contaminated the MAF sensor. Is there any contamination?	Yes	Go to the next step.
12		No	Inspect for cause.
13	Inspect the MAF sensor for contamination. Is there any contamination?	Yes	Replace the MAF sensor.
13		No	Go to the next step.
14	Is the engine compression correct?	Yes	Inspect the valve timing.
14	Is the engine compression correct?	No	Inspect for the cause.
15	Verify the test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, inspect related Service information and perform repair or diagnosis. - If the vehicle is repaired, the troubleshooting is completed. - If the vehicle not repaired or additional diagnostic information is not available, replace the PCM.