How To Test The EGR Valve (1993-1995 2.2L Buick Century, Oldsmobile Cutlass Ciera)

TEST 2: Applying Vacuum To The EGR Valve

In this test section, we'll manually apply a vacuum to the EGR valve with the engine idling.

Applying a vacuum to the EGR valve should cause two things to happen:

• The EGR valve's pintle should rise (causing the EGR valve to open and let exhaust gas recirculate into the intake manifold).
• The engine's idle should worsen.

If applying vacuum to the EGR valve does not affect the EGR valve's pintle and/or the engine's idle, one of the following issues is behind the problem:

• The EGR valve has a problem
• The EGR passages in the valve's adapter are blocked.
• The EGR passages in the intake manifold are blocked.

Let's get started:

1. 1

   Disconnect the vacuum line from the EGR valve.

2. 2

   Connect your vacuum pump to the EGR valve.

3. 3

   Start the engine and let it idle.

4. 4

   Apply vacuum to the EGR valve as you observe the engine's idle and the EGR valve's pintle (see image 2 of 2).

5. 5

   The engine's idle should get very rough and the EGR valve's pintle should rise.

6. 6

   Release the vacuum you applied to the EGR valve.

7. 7

   The engine's idle should return to normal and the EGR valve's pintle should lower (to the position it was in step 3).

Let's interpret your test result:

CASE 1: The engine's smooth idle became rough, and the pintle rose when you applied vacuum to the EGR valve. This is the correct test result.

This test result confirms several important things:

• The EGR valve is functioning correctly.
• The EGR passages in the valve's adapter block are open (not blocked with carbon).
• The EGR passages in the cylinder head and intake manifold are open (not blocked with carbon).

If an EGR valve diagnostic trouble code is illuminating the check engine light, the most likely cause is:

• The EGR valve system vacuum hoses are misrouted or broken.
• The EGR valve vacuum solenoid is bad.

CASE 2: The engine's idle was rough to begin with and became rougher, and the pintle rose when you applied vacuum to the EGR valve. This test result usually indicates the EGR valve is stuck open.

Your next test step is to go to: TEST 4: Making Sure The EGR Valve Pintle Is Not Stuck Open.

CASE 3: The engine's smooth idle DID NOT become rough, and the pintle DID NOT rise when you applied vacuum to the EGR valve. This test result tells you the EGR valve is bad and indicates one of two issues (with the EGR valve):

• The EGR valve's rubber diaphragm is bad.
• The EGR valve's pintle is stuck due to carbon buildup.

Remove and replace the EGR valve. Since you're removing the EGR valve, you can bench-test it: TEST 3: Bench Testing The EGR Valve.

CASE 3: The engine's smooth idle DID NOT become rough, but the pintle rose when you applied vacuum to the EGR valve. This test result generally tells you the EGR valve is OK but that the EGR passages are blocked somewhere between the EGR valve and the intake manifold.

To be more specific, this test result usually indicates one of two things:

• The EGR passages in the valve's adapter are blocked.
• The EGR passages in the intake manifold are blocked.

To further investigate this, go to: TEST 5: Checking For Blocked EGR Passages.

TEST 3: Bench Testing The EGR Valve

The EGR valve used in the 1993-1995 2.2L Buick Century and 1993-1995 2.2L Oldsmobile Cutlass Ciera is a negative back pressure EGR valve.

In plain English, this means that you and I can remove the EGR valve and bench-test it (off the vehicle) and check its performance.

The EGR valve's bench test should confirm that the valve's pintle and diaphragm move when you apply vacuum to the valve.

If the EGR valve's diaphragm is bad, applying vacuum will not affect it or the pintle (in other words: they won't move).

NOTE: To find out more about negative and positive back pressure EGR valves, see: How Can I Tell If I Have A Negative Or Positive Back Pressure EGR Valve?.

Let's get started:

1. 1

   Remove the EGR valve from its location.
   
   CAUTION: The EGR valve can get hot. You many need to let the engine cool down before removing it.

2. 2

   Connect your vacuum pump to the EGR valve.

3. 3

   Apply vacuum to the EGR valve.

4. 4

   You should see the EGR valve's diaphragm and pintle move up as you apply vacuum.

5. 5

   Hold (maintain) the vacuum applied to the valve for a few seconds.

6. 6

   The diaphragm and pintle should not move (return to their closed position) while you're maintaining vacuum to the EGR valve.

7. 7

   Release the vacuum you applied to the EGR valve.

8. 8

   You should see the EGR valve's diaphragm move back to its original position.

9. 9

   Repeat steps 3 thru 8 several times to make sure of your test results.

Let's interpret your test result:

CASE 1: The diaphragm/pintle moved up/down as you applied/released vacuum AND the diaphragm/pintle did not return to their closed position when you held the vacuum. This test result tells you that the EGR valve itself is OK (not defective).

If, in TEST 2, the engine's idle did not worsen when you applied vacuum to the EGR valve (with the engine running), you can conclude that either:

• The EGR valve adapter has its passages block with carbon.
• The intake manifold's EGR port is blocked with carbon.

If you suspect the EGR passages are blocked with carbon, go to: TEST 5: Checking For Blocked EGR Passages.

CASE 2: The EGR valve's diaphragm DID NOT move up/down as you applied/released vacuum to the valve. This test result confirms that the EGR valve is bad. Replace the EGR valve.