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Home >> Toyota >> 1999 >> RAV4 Base, 2D Utility, AWD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing - 4-Cylinder >> Emission Systems & Sub-Systems >> Exhaust Gas RECIRCULATION (EGR) System Test >> Tacoma & 4Runner
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Tacoma & 4Runner

  1. Remove cap and filter from top of EGR vacuum modulator. Ensure filter is clean and in good condition. Clean filter with compressed air (if necessary).
    2. NOTE: Filter must be installed in EGR vacuum modulator with coarse side facing upward, away from EGR vacuum modulator.
  2. Reinstall filter and cap. Using 3-way connector, install vacuum gauge in vacuum hose between top of EGR valve and EGR vacuum modulator. Perform STEP 1. See Fig 1. Start engine. Ensure engine idles smoothly to ensure proper seating of EGR valve.
  3. To test operation of EGR VSV with engine cold, ensure engine coolant temperature is less than 122°F (50°C). Increase and maintain engine speed at 3500 RPM. Ensure no vacuum reading is obtained on vacuum gauge with engine speed at 3500 RPM and EGR pipe is not hot.
  4. To test operation of EGR VSV and EGR vacuum modulator. Shut engine off. This test procedure may be performed by using scan tool to operate EGR VSV, or by connecting vacuum hose from port "Q" on EGR vacuum modulator to EGR valve. If using scan tool, go to next step. If scan tool is not available, go to step  6.
  5. Connect scan tool to data link connector No. 3. See Figure and Figure . Select ACTIVE TEST MODE on scan tool so EGR VSV is closed. Start engine. Operate engine at 3500 RPM again. Ensure a low vacuum reading is obtained on vacuum gauge with engine speed at 3500 RPM. Shut engine off. Remove scan tool. Go to step  8.
  6. Remove 3-way connector and small vacuum hose between port "Q" (single port) on EGR vacuum modulator and EGR valve. Perform STEP 2. See Fig 1. This 3-way connector and small vacuum hose goes from EGR valve and EGR vacuum modulator to EGR VSV. Install plug in vacuum hose to EGR VSV.
  7. Connect vacuum hose from port "Q" on EGR vacuum modulator to directly to EGR valve. See Figure. This will by-pass EGR VSV. Start engine. Operate engine at 3500 RPM again. Ensure a low vacuum reading is obtained on vacuum gauge with engine speed at 3500 RPM. Shut engine off. Reconnect vacuum hoses. Go to next step.
  8. To check EGR valve operation, remove and plug hose at EGR valve. Start engine. Using vacuum pump, apply vacuum directly to EGR valve with engine idling. Engine should run rough or stall. If EGR system does not operate as described, each individual component should be tested.
Fig 1: Installing Vacuum Gauge (Tacoma & 4Runner)
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