Inspections
| Action
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DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, fuel economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.
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Preliminary
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| • | Verify the following information: |
| - | Is the A/C ON or the Defroster mode ON full time? |
| - | Are the tires at the correct pressure? |
| - | Is there excessively heavy loads being carried? |
| - | Is the acceleration rate too much, too often? |
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Fuel System
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| • | Verify that each injector harness is connected to the correct injector and cylinder. Relocate the injector harnesses as necessary. |
| • | Inspect for foreign material accumulation in the throttle bore, coking on the throttle valve, or on the throttle shaft. |
| • | Inspect the following that may cause the engine to run rich: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. | - | Water intrusion in the HO2S connector |
| - | Engine oil contaminated by fuel |
| - | An evaporative emission (EVAP) canister purge condition |
| - | Vacuum hoses for splits, kinks, and proper connections |
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Sensor/System
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| • | Inspect the air intake system and crankcase for air leaks. |
| • | Inspect the crankcase ventilation valve for proper operation. Place a finger over the inlet hole in the valve end several times. The valve should snap back. If not, replace the valve. |
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Ignition System
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| • | Test for proper ignition voltage output with the
J 26792
Spark Tester. |
| • | An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to
Spark Plug Replacement
. |
| • | Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to
Spark Plug Inspection
for diagnosis of fouled spark plugs. |
| • | Visually and physically inspect the secondary ignition for the following conditions: |
| - | Spark plug wires arcing to ground |
| - | Spark plug wires for proper routing |
| • | Wetting down the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. |
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Engine Cooling System
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| • | Inspect the engine coolant level for being low. Refer to
Loss of Coolant
. |
| • | Inspect the engine thermostat for proper operation and for the correct heat range. |
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Engine Mechanical
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| • | Inspect the engine mechanical for the following conditions: |
| - | Sticking or leaking valves |
| • | Inspect the following components for incorrect basic engine parts. Refer to the appropriate procedures in Engine Mechanical for diagnosis procedures: |
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Additional
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| • | Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label. |
| • | Inspect the following components of the exhaust system for possible restrictions: |
| - | The exhaust system for damaged or collapsed pipes |
| - | The exhaust manifold for a collapsed inner wall |
| - | The mufflers for heat distress or possible internal failure |
| - | Compare the exhaust system back pressure on each side of engine. Refer to
Restricted Exhaust
. |
| • | Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in the engine speed parameter on the scan tool with little change in
actual engine RPM change indicates EMI is present. Inspect for high voltage components, near ignition control circuits, if a problem exists. |
| • | Inspect the intake and the exhaust manifold passages for casting flash. |
| • | Inspect the brake system for dragging or improper operation. Ensure that the vehicle operator does not drive with a foot on the brake pedal. |
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