Fixing EGR Valve Problems

When contemplating fixing EGR valve problems, it is interesting to know that, for the most part, the mechanical aspect is essentially the same for most EGR valves. The method of activation and control of flow varies immensely.

The EGR valve body is circular with the top and bottom being convex with rectangular cutouts in the bottom. The base of all the EGRs have two holes, one for the entrance of exhaust gas and one for the exhaust flow into the intake manifold (round). The round hole is closed by a pintle, which is a large tapered pin that moves vertically. When closed, the pintle will drop down and block the hole. As the pintle is lifted, it progressively allows more exhaust flow.

The EGR valves that do not have devices located on the top of them work completely on engine vacuum. This vacuum is modulated by an electrical device, usually a solenoid. The ones with devices on the top use no vacuum but are controlled by either stepper motors or electrical motors that lift the pintle for the desired flow. They have a position sensor that signals their position to the computer, which in turn regulates the pintle height.

The problems that will be encountered will come in three areas. The EGR valve will either have coking in the area of the pintle, causing the pintle to stick, a hole in the rubber vacuum diaphragm causing a vacuum leak and the pintle to remain stationery, or an electrical main power, position sensor or modulation problem.

The first thing to do is diagnose the problem. Start by pulling the vacuum line off the valve and installing a remote vacuum source such as a vacuum pump. A different vacuum line on the intake can be used that has a continuous vacuum with the engine running. Place a finger in one of the holes in the bottom of the valve so that the diaphragm can be felt. Apply the vacuum and feel if the diaphragm lifts up. If it does not, push up on the diaphragm. If the diaphragm can be lifted there is a hole in the diaphragm and the EGR is defective. If it cannot be lifted the pintle is coated with coke and can be cleaned and should once again be operational.

If the vacuum caused the diaphragm to rise, and the engine started to run rough, the problem is in the electrical circuit. Follow the vacuum line from the valve to the EGR vacuum solenoid. Using a voltmeter or test light, check for power at the electrical connector with the key on. If there is power, connect a jumper from the second wire, which is a ground, and momentarily touch a good ground. A distinct click should be heard or felt if you place your hand on it when it is grounded indicating that it is working. If there is no sound or cannot be felt, replace it. If it works there is a problem with the wiring or the EGR circuit in the computer.

Now the attention will be directed to the EGR valves with devices on top of them. These, as mentioned previously, are operated by the computer. Test these with a voltmeter. Pull the connector off and turn the key on. Check for battery voltage at one of the terminals. If this is not present, a wiring problem between this station is indicated. If battery power is present, plug the connector in and start the engine. Probe the connector for a second terminal to have 5 volts. This is the reference voltage. If it is present, the EGR must be replaced, if not the computer or connection is at fault.

If either type showed a sticking condition through the pressure test with a finger or the engine is running rough, remove the EGR. Turn it upside down and fill it with carburetor cleaner and let it sit for a half-hour. Use a small pocket screwdriver or similar device and scrape all the remaining coke off of the pintle and around the seat. Stick your finger in the access hole in the bottom of the EGR and work the diaphragm up and down to make sure it is loose. Clean the hole in the intake manifold so it is open. Replace the valve.

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