Exhaust Gas Recirculation: Testing and Inspection

EGR System:

EGR SOLENOID TEST

A faulty EGR system can cause ignition ping, rough idle, engine stalling, sags or hesitation, and/or lack of performance. It is important that this system be free from leaks. Any hoses that are cracked or leaking should be replaced.

Inspect all vacuum hoses and connections, and replace any that are cracked, hardened, or melted.

1. Start engine and allow to reach normal operating temperature.
2. Allow engine to run at normal idle speed and set the parking brake.
3. Verify that the EGR Solenoid has vacuum coming from its source (manifold vacuum).
4. Disconnect vacuum hose at the EGR Solenoid and connect a vacuum gauge in its place. Vacuum should be at least 15 in. Hg. If vacuum is low, check for twists, kinks or loose connections at the intake manifold or vacuum connectors. If vacuum is OK, remove gauge, reconnect the vacuum hose, and go to the next step.
5. Disconnect the vacuum hose from the EGR Solenoid output port and connect a vacuum gauge to the same port. Vacuum should be zero at this side of the solenoid.
6. If vacuum is zero, go to the next step. If vacuum is present, refer to COMPUTERIZED ENGINE CONTROLS for diagnosis of the system.
7. Disconnect the EGR Solenoid electrical connector, and verify that vacuum is now present.
8. If vacuum is present go to the CONTROL VALVE TEST, if vacuum is not present replace EGR Solenoid.



CONTROL VALVE TEST

1. Start engine and allow to reach normal operating temperature.
2. Allow engine to run at normal idle speed and set the parking brake.
3. Disconnect the EGR Solenoid electrical connector. Bypass the EGR transducer. Connect the output hose from the EGR Solenoid directly to the control valve nipple and verify that engine idle gets rough and may even stall.
4. If idle is not affected, go to the next step. If idle is affected, go to EGR TRANSDUCER TEST.
5. Disconnect EGR Solenoid output hose from control valve, and connect a hand held vacuum pump to the EGR control valve nipple.
6. Apply at least 12 in. Hg vacuum and see if idle stumbles.
7. If idle stumbles, check vacuum hoses and connectors for vacuum leaks. If the idle quality did not change, remove EGR control valve and check for a clogged control valve or intake passages, repair as necessary. If no clogging is present, replace EGR control valve.
8. If no leaks are found, go to EGR TRANSDUCER TEST.

EGR Transducer Test:

EGR TRANSDUCER TEST

1. Disconnect the transducer back-pressure line and the vacuum lines.
2. Plug the output port of the transducer, and connect a hand held air pump to the back-pressure port. Apply 1 to 2 lbs of air pressure.
3. Connect a hand held vacuum pump to the input port of the transducer and apply at least 12 in Hg vacuum.
4. Verify that the transducer holds vacuum, if it does not, it is defective and needs to be replaced.