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Electronic Sonic EGR Valve

  1. Connect vacuum gauge to valve. Apply 6 in. Hg vacuum to valve and trap. Vacuum should not drop more than 1 in. Hg in 30 seconds. If so, replace valve "O" ring or EVP sensor.
  2. As sonic valve is part of EEC system, check all circuitry as described in EEC article. Mechanical function can be checked as follows: Check vacuum lines for correct routing.
  3. Disconnect vacuum hose at valve and connect vacuum gauge to hose. Accelerate engine to 2000-2500 RPM and release throttle. Repeat 8-10 times and check for consistent response.
  4. If vacuum rises above zero, when engine is cold, diaphragm is leaking and valve should be replaced. With engine warm, vacuum should not rise above 15 in. Hg and should return to zero when throttle is released.
  5. If vacuum does not go to 15 in. Hg, check vacuum source and service. If vacuum does not return to zero or is inconsistent, solenoid is worn and should be replaced.
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