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EGR Function Testing - Lexus: Other Lexus LS II

Emission Applications 1 illustration ~2242 words

1990-93 ES250, ES300, GS300 & LS400 (Ported EGR Valve)

  1. Using a vacuum "T", connect a vacuum gauge between EGR vacuum hose and EGR valve (between EGR vacuum hose and vacuum switching valve on LS400). To ensure EGR valve is seating, start engine and check idle quality. If EGR valve is not seating, replace EGR valve.
  2. With coolant temperature at less than 104°F (40°C) on ES250, 95°F (35°C) on ES300, 122°F (50°C) on GS300, or 127°F (53°C) on LS400, vacuum gauge should indicate zero vacuum at 2500 RPM. Warm engine to normal operating temperature. Increase engine speed to 2500 RPM. Vacuum gauge should indicate low vacuum. If vacuum gauge does not indicate low vacuum, go to next step.
  3. Disconnect vacuum hose from port "R" of EGR vacuum modulator (lower of 2 ports on side of modulator). Connect port "R" directly to intake manifold using another vacuum hose. Vacuum gauge should indicate high vacuum with engine at 3500 RPM (ES250 and ES300), or 2500 RPM (GS300 and LS400).
  4. Engine may misfire slightly. Let engine idle. Remove vacuum gauge, and reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. Engine should run rough or stall. If results are as indicated, system is okay. If results are not as indicated, see EGR VACUUM MODULATOR CHECK.

EGR Vacuum Modulator Check (Except LS400 & SC400 Calif.)

  1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger (twin ports on side of modulator). Blow air into port "Q" (single port on side of modulator). Air should flow freely out of filter.
  2. Start and operate engine at 3500 RPM (ES250 and ES300) or 2500 RPM (GS300 and LS400). Block ports "P" and "R" with finger. Blow air into port "Q". Air should not flow out of filter. If air flows out of filter, replace EGR vacuum modulator.

1992-93 SC300 & SC400 (Ported EGR Valve)

  1. Connect tachometer to terminal IG of check connector. Using jumper wire, jumper check connector terminals TE1 and E1. Operate engine at 3500 RPM with transmission in Neutral. Remove jumper wire.
  2. With coolant temperature at or less than 113°F (45°C), no increase in engine RPM should be noted. With coolant temperature at least 122°F (50°C), engine RPM should increase.

EGR Vacuum Modulator Check (Except SC400 Calif.)

  1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger (twin ports on side of modulator). Blow air into port "Q" (single port on side of modulator). Air should flow freely out of filter.
  2. Start and run engine at 3500 RPM (ES250 and ES300) or 2500 RPM (GS300 and LS400). Block ports "P" and "R" with finger. Blow air into port "Q". Air should not flow out of filter. If air flows out of filter, replace EGR vacuum modulator.

1994-96 ES300

  1. Remove cap and filter from top of EGR vacuum modulator. Clean filter with compressed air. Install filter with coarse side facing upward. Install cap.
  2. Using a vacuum "T", connect a vacuum gauge in hose between EGR valve and Vacuum Switching Valve (VSV). To ensure EGR valve is seating, start engine and check idle quality.
  3. If idle is smooth, go to next step. If idle is rough, disconnect vacuum hose from EGR valve. If idle is smooth, check for problems in EGR vacuum control system. If idle is still rough, EGR valve is not seating. Replace EGR valve.
  4. Ensure engine coolant is less than 131°F (55°C). Connect Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1. Operate engine at 2800 RPM. There should be no vacuum indicated (no EGR occurs). If any vacuum is indicated, check EGR system components. If no vacuum is indicated, warm engine to 176°F (80°C). Check vacuum with engine running at 2800 RPM.
  5. If no vacuum or high vacuum is indicated, check EGR system components. If low vacuum (partial EGR) is indicated, disconnect vacuum hose from port "R" of EGR vacuum modulator. Connect a separate hose between port "R" and intake manifold.
  6. With engine running at 3500 RPM, high vacuum should be indicated (as volume of recirculated exhaust gas increases, engine will start to misfire). If no vacuum or low vacuum is indicated, check EGR system components. If high vacuum is indicated, disconnect jumper wire from DLC No. 1.
  7. Disconnect vacuum gauge. Reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. If engine runs rough or stalls, system is okay. If engine does not run rough or stall, replace EGR valve.

EGR Vacuum Modulator Check

  1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger (twin ports on side of modulator). Blow air into port "Q" (single port on side of modulator). Air should flow freely out of filter.
  2. Start and operate engine at 3500 RPM (ES250 and ES300) or 2500 RPM (GS300 and LS400). Block ports "P" and "R" with finger. Blow air into port "Q". Air should not flow out of filter. If air flows out of filter, replace EGR vacuum modulator.

1994-96 GS300 & SC300

  1. Remove cap and filter from top of EGR vacuum modulator. Clean filter with compressed air. Install filter with coarse side facing upward. Install cap.
  2. Using a vacuum "T", connect a vacuum gauge in hose between EGR valve and EGR vacuum modulator. To ensure EGR valve is seating, start engine and check idle quality.
  3. If idle is smooth, go to next step. If idle is rough, disconnect vacuum hose from EGR valve. If idle is smooth, check for problems in EGR vacuum control system. If idle is still rough, EGR valve is not seating. Replace EGR valve.
  4. Ensure engine coolant is less than 113°F (45°C). Run engine at 2500 RPM. There should be no vacuum indicated (no EGR occurs). If any vacuum is indicated, check EGR system components.
  5. If no vacuum is indicated, warm engine to 122°F (50°C). Check vacuum with engine running at 2500 RPM. If no vacuum or high vacuum is indicated, check EGR system components. If low vacuum (partial EGR) is indicated, disconnect vacuum hose from port "R" of EGR vacuum modulator.
  6. Connect a separate hose between port "R" and intake manifold. With engine running at 3500 RPM, high vacuum should be indicated (as EGR volume increases, engine should start to misfire). If no vacuum or low vacuum is indicated, check EGR system components. If high vacuum is indicated, disconnect vacuum gauge.
  7. Reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. If engine runs rough or stalls, system is okay. If engine does not run rough or stall, replace EGR valve.
  1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger (twin ports on side of modulator). Blow air into port "Q" (single port on side of modulator). Air should flow freely out of filter.
  2. Start and run engine at 3500 RPM (ES250 and ES300) or 2500 RPM (GS300 and LS400). Block ports "P" and "R" with finger. Blow air into port "Q". Air should not flow out of filter. If air flows out of filter, replace EGR vacuum modulator.

1994-96 LS400 & SC400

  1. Ensure coolant temperature is less than 127°F (53°C). Start engine. Shift transmission into Neutral. Block wheels. Connect Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1.
  2. Operate engine at 3500 RPM. Ensure coolant temperature is less than 127°F (53°C). While engine is running at 3500 RPM, disconnect jumper wire and observe engine RPM. If engine speed remains steady, go to next step. If engine speed does not remain steady, check for faulty EGR system components.
  3. Ensure engine coolant temperature is at least 131°F (55°C). Reconnect jumper wire between terminals TE1 and E1. While engine is running at 3500 RPM, disconnect jumper wire and observe engine RPM. If engine speed remains steady, EGR system is okay. If engine speed does not remain steady, check for faulty EGR system components.

EGR Vacuum Modulator Check (SC400 Fed. Only)

  1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger (twin ports on side of modulator). Blow air into port "Q" (single port on side of modulator). Air should flow freely out of filter.
  2. Start and operate engine at 3500 RPM (ES250 and ES300) or 2500 RPM (GS300 and LS400). Block ports "P" and "R" with finger. Blow air into port "Q". Air should not flow out of filter. If air flows out of filter, replace EGR vacuum modulator.

1996-97 LX450

  1. Ensure vacuum modulator filter is clean and in good condition. Clean filter with compressed air (if necessary). NOTE: EGR vacuum modulator filter must be installed with coarse side facing upward, away from EGR vacuum modulator.
  2. Using a "T" connector, install vacuum gauge in-line with vacuum hose at top of EGR valve. Start engine. Ensure engine runs or idles smoothly. Operate engine at 2500 RPM and with coolant temperature at less than 117°F (47°C). Vacuum should not be present and EGR pipe should not be hot.
  3. Continue running engine until coolant reaches normal operating temperature. Operate engine at 2500 RPM. Vacuum should now be present. Disconnect hose from port "R" of EGR modulator directly to intake manifold. High vacuum should now be present. NOTE: Engine should misfire due to large amounts of exhaust gas is being injected into intake manifold.
  4. Remove vacuum gauge and reconnect vacuum hose to EGR vacuum modulator. To check EGR valve, remove and plug vacuum hose at top of EGR valve. Using hand-held vacuum pump, apply vacuum to EGR valve with engine at idle. EGR valve should hold vacuum and engine should run rough or stall. If engine does not run rough or stall, check for faulty EGR valve or plugged EGR ports.
  5. Reconnect vacuum hose to EGR valve. A Diagnostic Trouble Code (DTC) may have been set in ECM while testing EGR system. Clear DTC.

GS 300 & SC 300

Note. DO NOT warm the engine until specified. Some testing must be performed when engine is cold.

  1. Remove cap and filter from top of EGR vacuum modulator. (Scheme 3) EGR vacuum modulator is mounted next to EGR valve. Clean filter with compressed air. Install filter with coarse side facing upward. Install cap.
  2. Using a vacuum "T", connect a vacuum gauge in hose between EGR valve and EGR vacuum modulator. To ensure EGR valve is seating, start engine and check idle quality.
  3. If idle is smooth, go to next step. If idle is rough, disconnect vacuum hose from EGR valve. If idle is smooth, check for problems in EGR vacuum control system. If idle is still rough, EGR valve is not seating. Replace EGR valve.
  4. Ensure engine coolant is less than 113°F (45°C). Block wheels. Apply parking brake. Start engine and allow it to idle. Firmly depress and hold parking brake pedal down. Shift transmission into "D" position. Slowly depress accelerator pedal, and raise engine speed to 1200-1600 RPM while observing vacuum gauge. There should be no vacuum indicated (no EGR occurs). If any vacuum is indicated, check EGR system components.
  5. If no vacuum is indicated, warm engine to 122°F (50°C). Again, slowly depress accelerator pedal and raise engine speed to 1200-1600 RPM and observe vacuum gauge. If no vacuum or high vacuum is indicated, check EGR system components. If low vacuum (partial EGR) is indicated, disconnect vacuum gauge.
  6. Reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. If engine runs rough or stalls, system is okay. If engine does not run rough or stall, replace EGR valve.

Scheme 3

Scheme 3
Scheme 3
  1. Start engine. With engine at normal operating temperature, remove and plug EGR vacuum hose.
  2. Using vacuum pump, apply vacuum to EGR valve with engine idling. Engine should run rough or stall. If not, check for defective EGR valve or plugged EGR passages.

For EGR function testing, see appropriate SYSTEM & COMPONENT TESTING article in the following publication: MITCHELL® ENGINE PERFORMANCE IMPORTED CARS, LIGHT TRUCKS & VANS supplement.

  1. 1997 (2 Of 3) - Page LEXUS 1-92.

LS 400 & SC 400

Note. DO NOT warm the engine until specified. Some testing must be performed when engine is cold.

  1. Remove "V" bank cover from top of engine. Ensure coolant temperature is less than 127°F (53°C). Block wheels. Start engine. Shift transmission into Neutral. Connect Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1.
  2. Run engine at 3500 RPM. Ensure coolant temperature is less than 127°F (53°C).
  3. While engine is running at 3500 RPM, disconnect jumper wire and observe engine RPM. If engine speed remains steady, go to next step. If engine speed does not remain steady, check for faulty EGR system components.
  4. Ensure engine coolant temperature is at least 131°F (55°C). Reconnect jumper wire between terminals TE1 and E1. While engine is running at 3500 RPM, disconnect jumper wire and observe engine RPM. If engine speed increases 100-300 RPM, EGR system is okay. If engine speed does not increase 100-300 RPM, check for faulty EGR system components.

ES300

Disconnect vacuum hose to EGR valve. Using a hand-held vacuum pump, apply 5 in. Hg to EGR valve. Vacuum should hold and EGR valve should remain open. Release vacuum, EGR valve should close. Check for binding or sticking EGR valve. Clean or replace as necessary.

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