EGR Vacuum Modulator
- Disconnect all hoses. Block ports "P" and "R". Apply air pressure to port "Q". See Fig 1. Air should pass through the air filter side of modulator freely.
- Operate engine at 2500 RPM. Repeat test procedures in step 1). Strong resistance of airflow should be felt. Replace EGR vacuum modulator if resistance is not felt. Reconnect vacuum hoses to proper locations