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HOMESERVICE MANUALSPONTIAC19846000 STEREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMEGR SYSTEM - V6 DIESEL (CALIF)SYSTEM TESTINGVACUUM CHECK
1984 Pontiac 6000 STE

Vacuum Check

1984 Pontiac 6000 STESECTION Vacuum Check

The Vacuum Circuit is monitored by the MAP sensor. A vacuum leak will cause a steady CEL that will not turn "OFF" by changing the throttle.

  1. This step checks for a vacuum source. Waiting 10 seconds allows the ECM to recognize a vacuum leak and shut EPR/EGR "OFF" if a leak is present. If vacuum is low, then becomes more than 10 in. Hg after 10 seconds (when CEL comes "ON") leak is most likely on valve side of solenoids.
  2. This step checks for leak in EGR vacuum circuit, which includes MAP sensor and vacuum connections. Vacuum should hold if a good circuit is present.
  3. This step checks for leak in EPR vacuum circuit. Vacuum should hold if circuit is good.
  4. This step checks if vacuum leak is in vacuum source circuit or EGR/EPR solenoid. By removing solenoid connections and plugging source side vacuum, normal reading for a source vacuum should be more than 10 in. Hg. This indicates that the leak is in the solenoid.
Fig 1: Vacuum Check
G13348
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
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