The EGR valve on the Honda Accord sits on top of the intake manifold at the rear of the engine. It introduces unburned exhaust gas back into the cylinders to help cool the cylinders and to reduce the amount of unburned gas exiting the exhaust. Unburned fuel that exits the exhaust gets expelled into the atmosphere, increasing pollution. The EGR valve is prone to caking up with soot, which hardens on the valve and causes the valve to stop working. If the build-up is not severe, you can clean and replace it.
Remove the vacuum lines and the wiring harness connector from the EGR valve. The vacuum line may or many not have a clamp. Loosen the clamp and pull the hose off, or simply pull the hose off if there is no clamp. Press the plastic tabs in on the electrical connector to remove the plug.
Unbolt and remove the two retaining bolts on the bottom of the valve. Lift the valve off the engine. Clean the gasket mating surfaces thoroughly, using a screwdriver if needed. Be careful not to gouge or scratch the gasket mating surfaces.
Inspect the EGR valve. If there is a small wire across the front of the valve, it cannot be cleaned. The wire is very thin and will be damaged by any pressure and/or chemicals. If there is no wire, continue.
Spray the inside of the EGR valve with carburettor cleaner, then shake the EGR valve out. Carefully scrape stubborn soot off with a screwdriver. Wipe out the inside of the valve with a rag, making sure it is completely dry before reinstalling the valve.
Place a new gasket on the intake's mating surface. Install the EGR valve and tighten the bolts firmly. Plug the vacuum line and the electrical connector in.