EGR (Exhaust Gas Recirculation) valves are devices that help reduce harmful emissions in modern vehicles. EGR valves first appeared in production vehicles in the 1970s and have become a requirement because of strict emission standards. Over time, EGR valves become clogged with carbon build-up and require cleaning. Every Mazda vehicle is equipped with an EGR valve and the cleaning procedure will be the same for all models, including the MX-5 Miata and the Mazda 3.
Removing the EGR Valve
Removing the EGR valve is the most difficult part of cleaning it, because it is difficult to access the bolts that mount it in place. For your protection, disconnect the negative battery cable before you begin the procedure. The EGR valve location will depend on which model Mazda you have, but it will always be located near the intake manifold and the throttle body. For front-wheel drive Mazda vehicles, this will usually be in the front part of the engine bay; for rear-wheel drive Mazda vehicles, this is usually the left side of the engine bay.
Disconnect the electrical connection from the valve, and then slip off the vacuum hoses. Every Mazda EGR valve has two vacuum hoses attached to it: one for incoming and one for outgoing. These vacuum hoses can be removed without tools.
Most EGR valves have two bolts in front that are easily seen. Use a standard socket wrench to remove these bolts. There is one bolt in the rear that can be difficult to access. Use a socket extension to help to you. The EGR mounting bolts are very secure, so it would be beneficial to use a penetrating lubricant, such as Liquid Wrench or Rust Buster. Once you have removed the valve, make sure you remove the gasket from the mount. The EGR valve gasket must be discarded and replaced.
Cleaning the EGR Valve
Use several hand towels and cotton swabs to clean the EGR valve. Use carbon cleaner to remove the carbon build-up from the EGR valve. Spray the carbon cleaner and let it sit for a few minutes to make cleaning the valve easier. Make sure the carbon cleaner is safe for catalytic converters or it may damage your converter. Open the valve and thoroughly clean the interior. Use the cotton swabs and hand towels to help remove the carbon from inside the valves.
Spray the carbon cleaner into the incoming and outgoing hose connections. Once the carbon cleaner loosens the carbon up, the most effective method of cleaner the hose connections is with the cotton swabs. A towel will be too difficult to fit into the small opening.
Use a small flashlight to peer inside the valve opening to make sure most of the carbon build-up is removed. Once you feel certain you have removed as much as you can, let the EGR valve dry for 30 minutes and reinstall it. Reinstallation is the reverse of removal.