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NO.14 POOR FUEL ECONOMY [WITHOUT WU-TWC]

id0103008020c6

14 | POOR FUEL ECONOMY
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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 timing belt • Contaminated MAF sensor • Improper engine compression • Exhaust system clogging 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. (See BEFORE REPAIR PROCEDURE.) (See AFTER REPAIR PROCEDURE.) Caution • If there is foreign material on the connecting area of the quick release connector, it might damage the connector or fuel pipe. To prevent this, disconnect the connector and clean the connecting area before connecting.

Diagnostic procedure

STEP | INSPECTION | RESULTS | ACTION
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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.
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.
No | No DTC is displayed: Go to the next step.
3 | Access ECT PID. Drive the vehicle while monitoring the PID. (See PCM INSPECTION [WITHOUT WU-TWC].) Is the PID within specification? | Yes | Go to the next step.
No | Inspect for coolant leakage, cooling fan and condenser fan operations or thermostat operation.
4 | Carry out a spark test. (See Spark Test.) Is a strong blue spark visible at each cylinder? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the spark test results.
5 | 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? (See FUEL LINE PRESSURE INSPECTION.) | Yes | Go to the next step.
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 the high pressure. Inspect for clogged fuel return line. Inspect the vacuum hose to the pressure regulator.
6 | Inspect VTCS operation. (See Variable Tumble Control System (VTCS) Operation Inspection.) Does VTCS function properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning parts.
7 | Inspect the variable valve timing control system operation. (See Variable Valve Timing Control System Operation Inspection.) Does the variable valve timing control system work properly? | Yes | Go to the next step.
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 Variable Intake-air System (VIS) Operation Inspection.) Does VIS function properly? | Yes | Go to the next step.
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.
No | Replace the PCV valve.
10 | Inspect for the restriction in the exhaust system. Is there any restriction? | Yes | Inspect the exhaust system.
No | Go to the next step.
11 | Inspect for a contaminated MAF sensor. Is there any contamination? | Yes | Go to the next step.
No | Inspect for the cause.
12 | Inspect the MAF sensor for contamination. Is there any contamination? | Yes | Replace the MAF sensor.
No | Go to the next step.
13 | Is the engine compression correct? (See COMPRESSION INSPECTION [ZJ, ZY].) | Yes | Inspect the valve timing. (See TIMING CHAIN REMOVAL/INSTALLATION [ZJ, ZY].)
No | Inspect for the cause.
14 | Verify test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, replace or reprogram the PCM.