TP-6903 5/16a Fuel System Troubleshooting 55
3.9. Poor Fuel Economy
Definition: Fuel economy, as measured by refueling
records, is noticeably lower than expected. Also, the
economy is noticeably lower than it was on this engine
at one time, as previously shown by refueling records.
Figure 3-11 Poor Fuel Economy Troubleshooting
Checks Action
Preliminary Checks
Check the air cleaner element (filter) for dirt or being plugged.
Visually check the vacuum hoses for splits, kinks, and proper connections.
Fuel System Checks
Check that the fuel pressure regulator is functioning properly.
Check the fuel system for leakage.
Sensor Checks
Check the TMAP sensor.
Ignition System Checks
Verify that the spark plugs are the correct type and properly gapped.
Remove the plugs and inspect them for the following conditions:
o Wet plugs (oil fouling).
o Cracks.
o Wear.
o Improper gap.
o Burned electrodes.
o Heavy deposits.
Check the ignition leads for the following items:
o Cracking.
o Hardness.
o Proper connections.
Cooling System Checks Check the engine thermostat to see if it is stuck open or for the wrong heat range.
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