I have done this and it does work. Remove the intake manifold. Be sure the valve you're working on is closed. Unplug the coils and turn over the engine until the valve is closed. Spray the cleaner onto the valve and valve stem. After the gunk has been dissolved by the cleaner, use shop rags and a Shop Vac to remove any debris before moving on to the next valve. Simply repeat the process with the remaining valves.