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Home >> Chevrolet >> 1988 >> Spectrum Express >> Repair and Diagnosis >> Engine Performance >> System >> Feedback Carburetor System >> Trouble Shooting >> System Performance Check
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System Performance Check

  1. Set parking brake. Place transmission in "P" (A/T) or "N" (M/T) and block wheels. Start engine. Disconnect and plug vacuum hose from charcoal canister and vent switch valve. Connect tachometer. Disconnect feedback solenoid at 3-pin carburetor connector. Ground feedback solenoid dwell terminal.
  2. Run engine at 3000 RPM. Keep throttle constant and reconnect feedback solenoid. Note RPM. If RPM dropped more than 100 RPM, go to step 3). If RPM dropped less than 100 RPM or increased, check feedback solenoid connections or repair carburetor. Remove ground from feedback solenoid dwell terminal before returning to idle.
  3. Disconnect idle set connector and connect dwell meter (6 cyl. scale) to feedback solenoid dwell terminal. Warm engine at part throttle until upper radiator hose is warm. Return engine to idle and note dwell.
  4. If dwell is fixed less than 15 degrees, go to TEST 1  . If dwell is fixed at 15-50 degrees, go to TEST 2  . If dwell is fixed greater than 50 degrees, go to TEST 3  . If dwell is varying, go to step 5).
  5. Check dwell at 3000 RPM. If dwell is between 10-50 degrees, check fuel cut-off system in TEST 7. If dwell is not between 10-50 degrees, check TPS or repair carburetor. If no trouble found, clear trouble codes.
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