COMPONENT TESTING

System Integrity Inspection

Check the EGR system hoses and connections for looseness, pinching, leaks, splitting, blockage, etc. Ensure that the EGR valve mounting bolts are not loose, or that the flange gasket is not damaged. If the system appears to be in good shape, proceed to the EGR vacuum test, otherwise repair the damaged components.

EGR System Vacuum Test

NOTE: The EVR solenoid has a constant internal leak; this is normal. There may be a small vacuum signal, however, it should be less than 1.0 in. Hg (3.4 kPa) of vacuum.

Start the engine and allow it to run until normal operating temperature is reached. With the engine running at idle, detach the vacuum supply hose from the EGR valve and install a vacuum gauge to the hose. The vacuum reading should be less than 1.0 in. Hg (3.4 kPa) of vacuum. If the vacuum is greater than that specified, the problem may lie with the EVR solenoid.

EVR Solenoid Test

1. Remove the EVR solenoid.
2. Attempt to lightly blow air into the EVR solenoid.
   1. If air blows through the solenoid, replace the solenoid with a new one.
   2. If air does not pass freely through the solenoid, continue with the test.
3. Apply battery voltage (approximately 12 volts) and a ground to the EVR solenoid electrical terminals. Attempt to lightly blow air, once again, through the solenoid.
   1. If air does not pass through the solenoid, replace the solenoid with a new one.
   2. If air does not flow through the solenoid, the solenoid is OK.

EGR Valve Function Test

1. Install a tachometer on the engine, following the manufacturer's instructions.
2. Detach the engine wiring harness connector from the Idle Air Control (IAC) solenoid.
3. Disconnect and plug the vacuum supply hose from the EGR valve.
4. Start the engine, then apply the parking brake, block the rear wheels and position the transmission in Neutral.
5. Observe and note the idle speed.

   NOTE: If the engine will not idle with the IAC solenoid disconnected, provide an air bypass to the engine by slightly opening the throttle plate or by creating an intake vacuum leak. Do not allow the idle speed to exceed typical idle rpm.

   Fig. 4: Some EGR valves may be tested using a vacuum pump by watching for diaphragm movement

6. Using a hand-held vacuum pump, slowly apply 5–10 in. Hg (17–34 kPa) of vacuum to the EGR valve nipple.
   1. If the idle speed drops more than 100 rpm with the vacuum applied and returns to normal after the vacuum is removed, the EGR valve is OK.
   2. If the idle speed does not drop more than 100 rpm with the vacuum applied and return to normal after the vacuum is removed, inspect the EGR valve for a blockage; clean it if a blockage is found. Replace the EGR valve if no blockage is found, or if cleaning the valve does not remedy the malfunction.