The EGR system recirculates part of the exhaust gas to lower the combustion chamber temperatures and reduce NOx emissions. The EGR system should be checked for proper operation every 60,000 miles. Check the filters on the vacuum modulator for contamination or damage and replace as necessary. Clean the filters with compressed air.
EGR Vacuum Modulator and Vacuum Switching Valve (VSV)
- Check the filter of the VSV for contamination of damage. Using compressed air, clean the filter of the valve.
- Using a 3-way connector, connect a vacuum gauge to the hose between the EGR valve and the EGR vacuum modulator.
- Start the engine and check that the engine starts and runs at idle.
- The coolant temperature should be below 135°F (57°C). Check that the vacuum gauge reads 0 at 2500 rpm (3500 rpm on the Van models).
- Let the engine reach normal operating temperature. Check that the vacuum gauge indication is approximately 2.76 in.Hg of vacuum at 2500 rpm (3500 rpm on the Van models).
- Check to see that the vacuum gauge reads 0 at idle.
- On the 1983-88 Cressida models, use the following procedure:
- Disconnect the vacuum hoses from ports P, Q and R of the EGR vacuum modulator. Plug off ports P and R.
- Blow compressed air into port Q. Check that the air passes through to the air filter side freely.
- Start the engine and maintain a speed of 2,500 rpm. Repeat the above test. Check that there is a strong resistance to air flow.
- If the vacuum modulator fails the inspection, replace it with a new one. Reconnect the vacuum hoses to the proper location.
- On the 1989-90 Cressida and Van Models, use the following procedure.
- Disconnect the vacuum hose from the EGR valve and tee a vacuum gauge inline.
- Start the engine and make sure it idles smoothly. With the engine cold-below 135°F (57°C)-the vacuum gauge should read zero at 2500 rpm (3500 on the Van models).
- Allow the engine to reach normal operating temperature and check that the vacuum gauge now indicates about 3 in. Hg at 2500 rpm (3500 rpm on the Van models). On Van models, the vacuum gauge should read zero at 5000 rpm.
- Disconnect the vacuum hose from the "R" port of the vacuum modulator, then connect the port directly to the intake manifold using another hose. The vacuum gauge should read high vacuum at 2500 rpm (3500 rpm on the Van models).
- If so, the EGR system is working properly. Disconnect the vacuum gauge and restore all disconnected vacuum hoses to their proper connections.
The engine should misfire slightly as a large amount of EGR gas enters the engine.
- On all models, inspect the EGR modulator valve operation by disconnecting the hoses from ports P, Q and R. Plug ports P and R, then blow air into port Q and check that air passes freely. Start the engine and hold the engine speed at 2500 rpm. Repeat the test and check that there is now a strong resistance to air flow. If not, replace the EGR vacuum modulator and retest. If so, restore the vacuum hoses to their proper connections.
- Check the vacuum switching valve (VSV) operation by applying battery voltage to the terminals and blowing through the valve. On Cressida models, the VSV should be open (air passes through) when energized and closed (no air passage) when power is removed. On The Van models, air should pass between the two vacuum ports when the VSV is energized, and from the back port to the air filter when power is removed. Any results other than these, replace the VSV and retest.
- Drain the coolant from the radiator into a suitable container. Remove the BVSV.
- Cool the BVSV to below 104°F (40°C) with cool water. Blow air into a hose that is connected to the BVSV and check that the BVSV is closed.
- Heat the BVSV to above 129°F (54°C) with hot water. Blow air into a hose that is connected to the BVSV and check that the BVSV is open.
- If the BVSV fails the inspection replace it. Apply a liquid sealer to the threads of the BVSV and reinstall it on the engine. Refill the radiator with coolant.