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

TEST 4: Making Sure The EGR Valve Pintle Is Not Stuck Open

A common problem with EGR valves is carbon blocking the valve's pintle from completely closing.

When carbon blocks the EGR valve's pintle from closing, exhaust gas is allowed to enter the intake manifold at all times.

In a few cases, the carbon will seize the pintle, and the pintle will no longer move (to open/close the valve) when the EGR valve gets vacuum from its vacuum regulator solenoid.

To find out if this is happening to the EGR valve on your vehicle, we need to remove it and blow compressed air into the valve's exhaust port to see if it comes out of the valve's intake air port.

Let's get started:

1. 1

   Remove the EGR valve from its location on the side of the cylinder head once the engine has cool down.

2. 2

   Turn the EGR valve over.

3. 3

   Visually check to see if the valve's pintle is stuck open.

4. 4

   Blow compressed air into the bore (that contains the pintle) and see if this air comes out the outlet.

5. 5

   Air should no pass thru to the other side.

Let's take a look at what your test results mean:

CASE 1: Air did not pass thru. This is the correct test result. Unfortunately, it tells you that the EGR valve's diaphragm is bad.

You can conclude that the EGR valve is bad and needs replacement if you have:

• Confirmed that the EGR valve IS NOT receiving vacuum when the engine is idling (TEST 1).
• Confirmed that the EGR valve's pintle DOES NOT rise and the engine's idle is unaffected when applying vacuum to the EGR valve (TEST 2).
• Confirmed that air DOES NOT pass thru the valve (this test section).

NOTE: You can re-use the same EGR valve gasket if it isn't damaged. Whether using the same gasket or a new one, you must install the gasket dry. In other words: DO NOT use any sealer (like RTV Silicone) on it.

CASE 2: Air passed from one port to the other. This test result tells you that the EGR valve's pintle is stuck open. Replace the EGR valve.

TEST 5: Checking For Blocked EGR Passages

If you've reached this point, you have confirmed:

• The EGR valve's vacuum hose IS NOT supplying vacuum to the valve when the engine is idling (TEST 1).
• The EGR valve's pintle and diaphragm rose when you applied vacuum to the valve, but the engine's idle DID NOT worsen (TEST 2).

It's not uncommon for the passages that channel the exhaust gas into the intake manifold to get blocked with carbon.

In this test section, we'll perform a very simple test that'll help us confirm whether or not the EGR passages are blocked.

IMPORTANT: If the engine has been running for any length of time and the EGR valve is hot, wait till the engine cools down completely before removing the EGR valve.

Let's get started:

1. 1

   Remove the EGR valve from its place on the engine.
   
   NOTE: Remove any and all parts, nuts, tools, or anything that may fall into the open ports on the EGR valve adapter.

2. 2

   Start the engine and let it idle for no more than 10 seconds.

3. 3

   After no more than 10 seconds, turn the engine off.

4. 4

   You'll see one of two results:
   
   1.) The engine started and ran with a very high idle and/or stalled.
   
   2.) The engine started and ran normally (no high or rough idle).

Let's interpret your test result:

CASE 1: The engine started and idled normally (no high or rough idle). This test result confirms that the exhaust gas recirculation passages are blocked, preventing exhaust gas from entering the intake manifold.

Your next steps are to remove the EGR adapter block and check it for carbon blockage (obstruction) and possibly even remove the intake manifold to check it for EGR passage blockage.

CASE 2: The engine started and idled high and/or the engine stalled. This is the correct and expected test result and tells you that the EGR passages ARE NOT blocked.

You can conclude that the EGR valve is bad if you have confirmed:

• The EGR valve's vacuum hose IS NOT supplying vacuum to the valve when the engine is idling (TEST 1).
• The EGR valve's pintle and diaphragm rose when (you applied vacuum to the valve), but the engine's idle DID NOT worsen (TEST 2).

How Can I Tell If I Have A Negative Or Positive Back Pressure EGR Valve?

All vehicles covered by this tutorial come equipped with a negative back pressure EGR valve.

Unfortunately, it's common for the EGR valve to get replaced with an aftermarket positive back pressure EGR valve.

You can most of the time tell what type of EGR valve you've got on your vehicle by looking at the numbers stamped on the EGR valve's diaphragm housing.

The numbers stamped on the EGR valve should have a trailing letter N or a letter P. The letter N indicates a negative back pressure EGR valve.

The image above shows an EGR valve stamped with the letter N indicating it's a negative back pressure EGR valve.

An EGR valve stamped with a trailing letter P indicates a positive back-pressure EGR valve.

Why should we care? Because only the negative back pressure EGR valves can be bench-tested off of the vehicle with a vacuum pump.

More 2.2L Buick Century And Oldsmobile Cutlass Ciera Test Tutorials

If this tutorial was helpful, be sure and take a look at all of the 2.2L Buick Century and Oldsmobile Cutlass Ciera diagnostic tutorials in this index:

• GM 2.2L Index Of Articles.

Here's a sample of the tutorials you'll find there:

• How To Test The Fuel Pump (1993-1996 2.2L Buick Century, Oldsmobile Cutlass Ciera).
• How To Test The TPS (1993-1996 2.2L Buick Century, Oldsmobile Cutlass Ciera).
• How To Test Engine Compression (1993-1996 2.2L Buick Century, Oldsmobile Cutlass Ciera).
• How To Test The MAP Sensor (1993-1996 2.2L Buick Century, Oldsmobile Cutlass Ciera).