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NO.14 POOR FUEL ECONOMY [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513)

BME010300103219

14 | Poor fuel economy
DESCRIPTION | • Fuel economy is unsatisfactory.
POSSIBLE CAUSE | • Contaminated air cleaner element • IMCC malfunction • Engine cooling system malfunction • Improper ATF level • Weak spark
• Poor fuel quality
• Erratic or no signal from CMP sensor
• 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 "BEFORE SERVICE PRECAUTION" and "AFTER SERVICE PRECAUTION" described in this manual.
  (See BEFORE SERVICE PRECAUTION [AJ].)
  (See AFTER SERVICE PRECAUTION [AJ].)

Diagnostic procedure

STEP | INSPECTION | ACTION
--- | --- | ---
1 | • Inspect the following:

  - Air cleaner element for contamination
  - ATF level
  - Fuel quality
  - Coolant level

• 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. • Turn the ignition switch to the ON position (Engine off). • Retrieve any DTCs. • Is "PASSED" displayed? | Yes | No DTC is displayed: • Go to the next step.
No | DTC is displayed: • Go to the applicable DTC inspection. (See DTC TABLE [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513).)
3 | • Access ECT PID. • Drive the vehicle while monitoring PID. (See PCM Inspection Using the WDS or Equivalent.) • Is PID within the specification? | Yes | Go to the next step.
No | Inspect for coolant leakage. Inspect the cooling fan operations or the thermostat operations.
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 installed improperly. • Trigger wheel damage on camshaft • Open or short circuit on CMP sensor
• Open or short circuit between CMP sensor and PCM terminal 85 or 86
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 filter 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 [AJ].) | Yes | Go to the next step.
No | Zero or low: • Inspect the fuel pump circuit. • Inspect for open fuel pump relief valve. • Inspect for fuel leakage inside the pressure regulator. • Inspect for clogged main fuel line. High:
• Inspect the pressure regulator for high pressure cause.
• Inspect for clogged fuel return line.
6 | • Inspect the IMCC operation. (See INTAKE MANIFOLD COMMUNICATION CONTROL (IMCC) ACTUATOR INSPECTION [AJ] (VIN: JMZ LW19J7*# 300001-, JM0 LW10J300 300001-301405, JM6 LW10J300 300001-, JM8 LW28J**# 300001-301513).) • Does the IMCC work properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part.
7 | • Remove and shake the PCV valve. • Does the PCV valve rattle? | Yes | Go to the next step.
No | Replace the PCV valve.
8 | • Inspect for restriction in the exhaust system. • Is there any restriction? | Yes | Inspect the exhaust system.
No | Go to the next step.
9 | • Is the brake system functioning properly? | Yes | Go to the next step.
No | Inspect for cause.
10 | • Inspect the MAF sensor for contamination. • Is there contamination? | Yes | Replace the MAF sensor.
No | Go to the next step.
11 | • Is the engine compression correct? | Yes | Inspect the valve timing.
No | Inspect for cause.
12 | • Verify test results.

  - If normal, return to diagnostic index to service any additional symptoms.
  - If malfunction remains, inspect related Service Information and perform repair or diagnosis.

  • If vehicle is repaired, troubleshooting completed.
  • If vehicle is not repaired or additional diagnostic information is not available, replace or reprogram the PCM.