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NO.14 POOR FUEL ECONOMY [L3]

BME010300000W16

14 | POOR FUEL ECONOMY
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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
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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. (See PCM INSPECTION [L3].) 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? (See FUEL LINE PRESSURE INSPECTION [L3].) | 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. (See Variable Tumble Control System (VTCS) Operation Inspection.) Does VTCS work properly? | Yes | Go to next step.
No | Repair or replace malfunctioning parts.
7 | Inspect for VIS operation. (See VIS Operation Inspection.) 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.