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Home >> Ford >> 1984 >> Bronco II Automatic >> Repair and Diagnosis >> Engine Performance >> System >> EGR System >> Testing >> EGR Valve With Integral Back Pressure Transducer >> Valve Function Test
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Valve Function Test

  1. Clamp drive socket wrench into tailpipe. Socket outside diameter should be about 1/16" less than tailpipe inside diameter. Socket drive hole should be covered and socket should be inserted into tailpipe with open end facing out to ensure proper back pressure.
  2. Do not block tailpipe fully or run engine faster than idle for prolonged periods of time. Be sure to remove socket from tailpipe at end of test.
  3. Idle engine and apply vacuum to EGR valve gradually. EGR valve diaphragm should move smoothly and rough idle should occur. Trap 6 in. Hg vacuum in EGR valve and hold. Vacuum should drop more than 1 in. Hg in 30 seconds.
  4. If vacuum does not drop or diaphragm does not move, replace valve. If diaphragm moves but idle does not change, remove valve and clean inlet and outlet ports with wire brush.
  5. If valve is suspected of sticking, remove valve from engine. Cycle valve by pressing carefully with fingers against lower transducer plate. If valve sticks open when fingers are released, replace valve. If valve does not stick and correct vacuum signal is present at valve, check valve for carbon deposits and clean as necessary.
  6. If engine has less than 6000 miles on it, is idling rough, and valve is suspected of being open, remove valve and check valve for foreign material. Tap base of valve on table while holding valve open with fingers. If foreign material falls from valve, make sure valve closes and reassemble valve to engine.
  7. Reconnect vacuum line and check for rough idle. If rough idle continues and valve is still sticking, replace valve. If valve is not sticking, rough idle problem is not in EGR system.
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