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NO.14 POOR FUEL ECONOMY [L3]

BME010300103252

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 SERVICE PRECAUTION" and "AFTER PRECAUTION" described in this manual.
  (See BEFORE SERVICE PRECAUTION [L3].)
  (See AFTER SERVICE PRECAUTION [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 the following: • Air cleaner element for contamination • 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. Are there any DTCs displayed? | Yes | DTC is displayed: Go to the applicable DTC inspection. (See DTC TABLE [L3].)
No | No DTC is displayed: Go to the next step.
3 | Access ECT PID. Drive the vehicle while monitoring PID. (See PCM INSPECTION [L3].) Is PID within the specification? | Yes | Go to the next step.
No | Inspect for coolant leakage, the cooling fan and condenser fan operations or the thermostat operation.
4 | Is 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 part.
If normal, go to the next step.
No | Inspect the following: • High-tension leads • Ignition coil and connector
5 | Install a fuel pressure gauge between the fuel pipe and the fuel distributor. Start the 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 the next step.
No | Zero or low: Inspect for clogged fuel line. If normal, replace the fuel pump unit (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L3].) High:
Replace the fuel pump unit.
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L3].)
6 | Inspect for the VTCS operation. (See Variable Tumble Control System (VTCS) Operation Inspection.) Does the VTCS work properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part.
7 | Inspect for the VIS operation. (See VIS Operation Inspection.) Does the VIS work properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part.
8 | Remove and shake the PCV valve. Does the PCV valve rattle? | Yes | Go to the next step.
No | Replace the PCV valve.
9 | Inspect for restriction in the exhaust system. Is there any restriction? | Yes | Inspect the exhaust system.
No | Go to the next step.
10 | Inspect for contaminated the MAF sensor. Is there any contamination? | Yes | Go to the next step.
No | Inspect for cause.
11 | Inspect the MAF sensor for contamination. Is there any contamination? | Yes | Replace the MAF sensor.
No | Go to the next step.
12 | Is the engine compression correct? | Yes | Inspect the valve timing.
No | Inspect for cause.
13 | Verify test results. • If normal, return to diagnostic index to service any additional symptoms. • If malfunction remains, replace PCM.