NO.14 POOR FUEL ECONOMY [L3]

BME010300000W16

14

POOR FUEL ECONOMY

DESCRIPTION

Fuel economy is unsatisfactory.

POSSIBLE CAUSE

• Contaminated air cleaner element
• VIS malfunction
• Engine cooling system malfunction
• Weak spark
• Poor fuel quality
• Erratic or no signal from CMP sensor
• Clutch slippage
• VTCS malfunction
• 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 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 [L3].)
(See AFTER REPAIR PROCEDURE [L3].)
Caution
• Disconnecting/connecting quick release connector without cleaning it may possibly 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 following:
• Air cleaner element for contamination
• Fuel quality
• Coolant level
• Brake dragging
• Clutch slippage
Are all items okay?
Yes
Go to next step.
No
Service as necessary.
Repeat Step 1.
2
Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory, KOEO and KOER DTCs.
Are there any DTCs displayed?
Yes

DTC is displayed:

Go to appropriate DTC test.
No

No DTC is displayed:

Go to next step.
3
Access ECT PID.
Drive vehicle while monitoring PID.
Is PID within specification?
Yes
Go to next step.
No
Inspect for coolant leakage, cooling fan and condenser fan operations or thermostat operation.
4
Is strong blue spark visible at each disconnected high-tension lead while cranking engine?
Yes
Inspect for 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 malfunctioning parts.
If okay, go to next step.
No
Inspect following:
• High-tension leads
• Ignition coil and connector
5
Install fuel pressure gauge between fuel pipe and fuel distributor.
Start engine and run it at idle.
Measure fuel line pressure at idle.
Is fuel line pressure correct at idle?
Yes
Go to next step.
No

Zero or low:

Inspect for clogged fuel line.
If okay, replace fuel pump unit

High:

Replace fuel pump unit.
6
Inspect for VTCS operation.
Does VTCS work properly?
Yes
Go to next step.
No
Repair or replace malfunctioning parts.
7
Inspect for VIS operation.
Does VIS work properly?
Yes
Go to next step.
No
Repair or replace malfunctioning parts.
8
Remove and shake PCV valve.
Does PCV valve rattle?
Yes
Go to next step.
No
Replace PCV valve.
9
Inspect for restriction in the exhaust system.
Is there any restriction?
Yes
Inspect exhaust system.
No
Go to next step.
10
Inspect for contaminated MAF sensor.
Is there any contamination?
Yes
Go to next step.
No
Inspect for cause.
11
Inspect MAF sensor for contamination.
Is there any contamination?
Yes
Replace MAF sensor.
No
Go to next step.
12
Is engine compression correct?
Yes
Inspect valve timing.
No
Inspect for cause.
13
Verify test results.
• If okay, return to diagnostic index to service any additional symptoms.
• If malfunction remains, replace PCM.