GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Important: Driving habits affect fuel economy. Check the owner's driving habits by asking the following questions:

   • Is the A/C system, i.e. defroster mode, turned on all the time?
   • Are the tires at the correct air pressure?
   • Have excessively heavy loads been carried?
   • Does the driver accelerate too much and too often? Suggest the driver read the section in the owner's manual about fuel economy.

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.

1

Were the Preliminary Checks performed?

Go to Step 2

Go to Symptoms - Engine Controls

2

  1. Inspect the air filter for excessive contamination.
  2. Inspect for fuel system leaks.

Are all needed inspections complete?

Go to Step 3

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3

  1. Inspect the spark plugs for excessive wear, insulation cracks, improper gap, or heavy deposits.
  2. Replace any faulty spark plugs.
  3. Inspect the ignition wires for cracking, hardness, and proper connections.

Did you find and correct the condition?

Go to Step 4

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4

  1. Inspect the engine coolant level.
  2. Inspect the thermostat for being always open or for an incorrect heat range.
  3. Replace the thermostat as needed.

Did you find and correct the condition?

Go to Step 5

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5

  1. Inspect the transaxle shift pattern. Ensure all transaxle gears are functioning.
  2. Inspect the torque converter clutch (TCC) operation with a scan tool. The scan tool should indicate RPM drop when the TCC is commanded ON.
  3. Inspect for proper calibration of the speedometer.
  4. Inspect the brakes for dragging.
  5. Inspect the cylinder compression.
  6. Repair, replace, or adjust any components as needed.

Did you find and correct the condition?

System OK

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