NO.14 POOR FUEL ECONOMY [LF, L3]


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 (if equipped) • 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 • Improper adjustment of variable resister (Leaded gasoline model) Warning The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read following warnings before performing 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 "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual. (See BEFORE REPAIR PROCEDURE [LF, L3].) (See AFTER REPAIR PROCEDURE [LF, L3].) Caution • Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and the 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 • Fuel quality • Coolant level • Brake dragging • Clutch slippage • Variable resister adjustment (Leaded gasoline model) (See Leaded Fuel Models) 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. Are 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 the ECT PID. Drive the vehicle while monitoring the PID. (See PCM INSPECTION [LF, L3].) Is the PID within the specification?	Yes	Go to the next step.
3		No	Inspect for coolant leakage, cooling fan and condenser fan operations or thermostat operation.
4	Is a strong blue spark visible at each disconnected high-tension lead while cranking the engine?	Yes	Inspect for the following: • Spark plugs malfunction • CMP sensor is improperly installed. • Trigger wheel damage on camshaft • Open or short circuit on CMP sensor • Open or short circuit between CMP sensor and PCM terminal 2J or 2M Repair or replace the malfunctioning parts. If normal, go to the next step.
4		No	Inspect the following: • High-tension leads • Ignition coil and connector
5	Install a fuel pressure gauge between fuel pipe and fuel distributor. Start engine and run it at idle. Measure the fuel line pressure at idle. Is the fuel line pressure correct at idle? (See FUEL LINE PRESSURE INSPECTION [LF, L3])	Yes	Go to the next step.
5		No	Zero or low: Inspect for a clogged fuel line. If normal, replace the fuel pump unit High: Replace the fuel pump unit.
6	Inspect the VTCS operation. (See Variable Tumble Control System (VTCS) Operation Inspection.) Does VTCS function properly?	Yes	Go to the next step.
6		No	Repair or replace the malfunctioning parts.
7	Note • The following test should be performed for vehicles with the variable valve timing control system. Go to the next step for vehicles without the variable valve timing control system. Inspect the variable valve timing control system operation. (See Variable Valve Timing Control System Operation Inspection (L3 Engine Models).) Does the variable valve timing control system function properly?	Yes	Go to the next step.
7		No	Repair or replace the malfunctioning parts.
8	Note • The following test should be performed for vehicles with VIS. Go to the next step for vehicles without VIS. Inspect for VIS operation. (See VIS Operation Inspection (L3 Engine Models).) Does VIS work properly?	Yes	Go to the next step.
8		No	Repair or replace the malfunctioning parts.
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	Inspect for restriction in the exhaust system. Is there any restriction?	Yes	Inspect the exhaust system.
10		No	Go to the next step.
11	Inspect for a contaminated MAF sensor. Is there any contamination?	Yes	Go to the next step.
11		No	Inspect for the cause.
12	Inspect the MAF sensor for contamination. Is there any contamination?	Yes	Replace the MAF sensor.
12		No	Go to the next step.
13	Is the engine compression correct?	Yes	Inspect the valve timing.
13	Is the engine compression correct?	No	Inspect for the cause.
14	Verify the test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, replace the PCM.