This tutorial will help you test the EGR valve on the 4.3L V6 engine with TBI fuel injection. No scan tool is required for any of the tests.
You'll quickly determine if the EGR valve is good or bad on your 4.3L V6 TBI Chevrolet S10 pickup, GMC S15 pickup or GMC Sonoma.
TBI = Throttle Body Injection
Contents of this tutorial:
- Symptoms Of A Bad EGR Valve.
- Important Testing Tips.
- What Tools Do I Need To Test The EGR Valve.
- TEST 1: Checking For Continuous Vacuum To EGR Valve.
- TEST 2: Applying Vacuum To The EGR Valve.
- TEST 3: Manually Pushing The EGR Valve's Diaphragm.
- TEST 4: Checking For Blocked EGR Passages.
- EGR Valve Code Keeps Coming Back
You can find this tutorial in Spanish here: Cómo Probar La Válvula EGR (1988-1995 4.3L TBI Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 4.3L V6 TBI Chevrolet S10 Pickup: 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995.
- 4.3L V6 TBI GMC S15 Pickup: 1988, 1989, 1990.
- 4.3L V6 TBI GMC Sonoma: 1991, 1992, 1993, 1994, 1995.
NOTE: You can find the EVRV solenoid test here:
Symptoms Of A Bad EGR Valve
The EGR valve allows a metered amount of exhaust gas into the intake manifold when it receives vacuum from the EGR vacuum solenoid.
The exhaust gas entering the intake manifold cools the combustion temperature in the cylinders to reduce the amount of oxides of nitrogen generated in the process.
The EGR valve must only allow exhaust gas recirculation if the following three conditions are met:
- The engine has reached normal operating temperature.
- The engine is under load.
- The fuel injection computer commands the EGR solenoid to supply vacuum to the EGR valve.
When the engine is idling, the EGR valve should be closed, thus preventing any exhaust gas from entering the intake manifold.
Depending on the nature of the EGR system failure you may or may not notice any engine performance issues when the fuel injection computer lights up the check engine light with an EGR system diagnostic trouble code.
When an EGR valve system failure occurs, the fuel injection computer usually sets an EGR system diagnostic trouble code. If it does, you'll see the following OBD I diagnostic trouble code:
- Code 32: EGR System Problem.
You'll also see one or more of the following symptoms:
- Rough idle.
- Bad gas mileage.
- Engine knock (pinging).
- Engine hesitation when accelerating the vehicle.
Important Testing Tips
TIP 1: The EGR valve can get very hot (when the engine is running). Start the EGR valve test with a cold engine.
TIP 2: You may need to remove the EGR valve to test it. You can reuse the same EGR valve gasket if it isn't damaged.
Whether you reuse the same gasket or install a new one, you must install the gasket dry. In other words: DO NOT use any sealer (like RTV Silicone) on it.
What Tools Do I Need To Test The EGR Valve
The two tools that will make testing the EGR valve a breeze is a handheld vacuum pump and a telescoping mirror.
If you don't have a vacuum pump, you can borrow one from your local auto parts store (for a small deposit that they'll return to you once you return the tool -AutoZone, O'Reilly Auto Parts).
If you'd like to buy a vacuum pump, this is my recommendation: Actron CP7835 Vacuum Pump (at: amazon.com).
TEST 1: Checking For Continuous Vacuum To EGR Valve
As mentioned earlier, when the EGR valve receives vacuum, it opens and allows exhaust gas into the intake manifold.
Without vacuum, the EGR valve remains in its closed position, preventing exhaust gases from entering the intake manifold.
The focus of our first test is check if the EGR valve is receiving continuous vacuum from its vacuum line while the engine is running.
The correct test result is that the vacuum line should not have vacuum present with the engine idling.
IMPORTANT: Be careful and take all necessary safety precautions while working around a running engine.
OK, let's start:
- 1
Disconnect the vacuum hose that connects to the EGR valve vacuum port.
Leave the other end that connects to the EGR vacuum solenoid connected to it. - 2
Connect a vacuum gauge to the vacuum hose you just disconnected from the EGR valve.
NOTE: If you don't have a vacuum gauge, don't panic. You can still check to see if vacuum is present in the vacuum hose. - 3
Start the engine and let it idle.
- 4
The vacuum hose you just disconnected should not have vacuum.
Let's take a look at what your test results mean:
CASE 1: Vacuum WAS NOT present. This is the correct and expected test result since manifold vacuum should NOT be present when the engine is idling.
The next step is to apply vacuum to the EGR valve while the engine is idling. For this test, go to: TEST 2: Applying Vacuum To The EGR Valve.
CASE 2: Vacuum was present. This is a problem since vacuum should not be present when the engine is idling.
Vacuum present in the vacuum hose is usually caused by one of the following issues:
- The EGR vacuum solenoid is defective (this solenoid is known as the EVRV solenoid).
- The vacuum hose is attached to the wrong port on the EGR vacuum solenoid.
Your next step is to check that the vacuum hose connected to the EGR valve is routed correctly. If the vacuum hose is going to the right place (the EGR vacuum solenoid), your next step is to test the EGR vacuum solenoid (known as the EVRV solenoid).
