NO.14 POOR FUEL ECONOMY [YF (2.0L Zetec)]


14	POOR FUEL ECONOMY
DESCRIPTION	Fuel economy is unsatisfactory.
POSSIBLE CAUSE	• Contaminated air cleaner element • Variable intake-air control malfunction • Engine cooling system malfunction • Weak spark • Poor fuel quality • Erratic or no signal from CMP sensor • Clutch slippage (MTX) • Improper ATF level (ATX) • Variable tumble control malfunction • Improper coolant level • Inadequate fuel pressure • Spark plug malfunction • PCV valve malfunction • Brake dragging • Improper valve timing due to timing belt run-out • Contaminated MAF sensor • Improper engine compression • Exhaust system clogging Warning The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read the following warnings before performing any fuel system-related procedures: • 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" described in this manual. (See BEFORE SERVICE PRECAUTION [YF (2.0L Zetec)].) (See AFTER SERVICE PRECAUTION [YF (2.0L Zetec)].) Caution • Disconnecting/connecting quick release connectors without cleaning them may possibly cause damage to the fuel pipe or quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.


STEP	INSPECTION	RESULTS	ACTION
1	Inspect the following: • Air cleaner element for contamination • ATF level (ATX) • Fuel quality • Coolant level • Brake dragging • Clutch slippage (MTX) 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 using the WDS or equivalent. Are any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC inspection. (See DTC TABLE [YF (2.0L Zetec)].)
2		No	No DTC is displayed: Go to the next step.
3	Access the ECT PID. Drive the vehicle while monitoring the PID. (See PCM INSPECTION [YF (2.0L Zetec)].) Is PID within specification?	Yes	Go to the next step.
3		No	Inspect for coolant leakage, cooling fan and thermostat operation.
4	Perform the spark test. (See Spark Test.) Is a strong blue spark visible at each cylinder?	Yes	Go to the next step.
4		No	Repair or replace malfunctioning part according to spark test result.
5	Inspect the following ignition control system related parts: • Spark plug (heat range) • CMP sensor installation • CMP sensor trigger wheel damaged (on camshaft) • Open or short circuit on CMP sensor • Open or short circuit between CMP sensor terminal 1 and PCM terminal 85 • Open or short circuit between CMP sensor terminal 2 and GND Are all items okay?	Yes	Go to the next step.
5		No	Repair or replace malfunctioning part.
6	Install a fuel pressure gauge to the fuel line 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 [YF (2.0L Zetec)].)	Yes	Go to the next step.
6		No	Low: Inspect the fuel line for clogging. • If there is no malfunction, replace the fuel pump unit (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].)
7	Inspect variable tumble control operation. Does the variable tumble control function properly?	Yes	Go to the next step.
7		No	Repair or replace the malfunctioning part.
8	Inspect variable intake-air control operation. Does the variable intake-air control function properly?	Yes	Go to the next step.
8		No	Repair or replace the malfunctioning part.
9	Remove and shake the PCV valve. Does the PCV valve rattle?	Yes	Go to the next step.
9	Remove and shake the PCV valve. Does the PCV valve rattle?	No	Replace the PCV valve.
10	Visually inspect the exhaust system part. Is there any deformed exhaust system part?	Yes	Replace the suspected part.
10		No	Go to the next step.
11	Inspect the MAF sensor for contamination. Is there any contamination?	Yes	Replace the MAF sensor.
11		No	Go to the next step.
12	Is engine compression correct?	Yes	Inspect valve timing.
12	Is engine compression correct?	No	Inspect for cause.
13	Verify test results. • If normal, return to the diagnostic index to service any additional symptoms. (See ENGINE SYMPTOM TROUBLESHOOTING [YF (2.0L Zetec)].) • If any malfunction remains, inspect related service information and, repair or diagnosis accordingly. - If the vehicle is repaired, troubleshooting completed. - If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [YF (2.0L Zetec)].)