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NO.14 POOR FUEL ECONOMY [AJ] (VIN: JM0 LW10J300 301406-, JMZ LW69J7*# 307683-, JM8 LW28J**# 301514-, JM8 LW28A**# 301514- (Assumed))

BME010300000W10

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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.
  (See BEFORE SERVICE PRECAUTION [AJ].)
  (See AFTER SERVICE PRECAUTION [AJ].)

Diagnostic procedure

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

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

• Are all items normal?
Yes
Go to next step.
No | Service as necessary. Repeat Step 1.
2 | • Connect WDS or equivalent to DLC-2. • Turn ignition switch to ON (Engine OFF). • Retrieve any DTCs. • Is "PASSED" displayed? | Yes | No DTC is displayed: • Go to next step.
No | DTC is displayed: • Go to appropriate DTC test.
3 | • Access ECT PID. • Drive vehicle while monitoring PID. (See PCM Inspection Using the SST (WDS or equivalent).) • Is PID within specification? | Yes | Go to next step.
No | Inspect for coolant leakage. Inspect cooling fan operations or thermostat operations.
4 | • Perform spark test. (See Spark Test.) • Is strong blue spark visible at each cylinder? | Yes | Inspect for 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 2 or 28
Repair or replace malfunctioning part.
• If normal, go to next step.
No | Repair or replace malfunctioning part according to spark test results.
5 | • Install fuel pressure gauge between fuel filter 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 [AJ].) | Yes | Go to next step.
No | Zero or low: • Inspect fuel pump circuit. • Inspect for open fuel pump relief valve. • Inspect for fuel leakage inside pressure regulator. • Inspect for clogged main fuel line. High:
• Inspect pressure regulator for high pressure cause.
• Inspect for clogged fuel return line.
6 | • Inspect IMCC operation. (See INTAKE MANIFOLD COMMUNICATION CONTROL (IMCC) ACTUATOR INSPECTION [AJ] (VIN: JM0 LW10J300 301406-, JMZ LW69J7*# 307683-, JM8 LW28J**# 301514-, JM8 LW28A**# 301514- (Assumed)).) • Does IMCC work properly? | Yes | Go to next step.
No | Repair or replace malfunctioning part.
7 | • Remove and shake PCV valve. • Does PCV valve rattle? | Yes | Go to next step.
No | Replace PCV valve.
8 | • Inspect for restriction in the exhaust system. • Is there any restriction? | Yes | Inspect exhaust system.
No | Go to next step.
9 | • Is brake system functioning properly? | Yes | Go to next step.
No | Inspect for cause.
10 | • Inspect MAF sensor for contamination. • Is there any contamination? | Yes | Replace MAF sensor.
No | Go to next step.
11 | • Is engine compression correct? | Yes | Inspect 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 PCM.