Spectrum 3.0L GM - Page 46

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POOR FUEL ECONOMY
Checks Action
DEFINITION: Fuel economy, as measured by refueling records, is noticeably lower than expected.
Also, the economy is noticeably lower than it was on this vehicle at one time, as previously shown by
refueling records.
Preliminary Checks
 Check the air cleaner element (filter) for dirt or being plugged.
 Visually check the vacuum hoses for splits, kinks, and proper connec-
tions.
 Properly inflated tires.
Check the operators driving habits for the following:
 Excessive idling or stop and go driving.
 Carrying of very heavy loads.
 Rapid acceleration.
 Suggest to the owner to fill the fuel tank and to recheck the fuel economy
and/or suggest that a different operator use the equipment and record the
results.
Fuel System Checks
 Check the Regulator fuel pressure. Refer to Fuel System Diagnosis.
 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:
 Wet plugs (oil fouling).
 Cracks.
 Wear.
 Improper gap.
 Burned electrodes.
 Heavy deposits.
Check the ignition wires for the following items:
 Cracking.
 Hardness.
 Proper connections.
Cooling System
Checks
Check the engine thermostat to see if it is stuck open or for the wrong heat
range.