Folks, I'm looking for the collective wisdom to trouble-shoot and solve this problem. The tach works, meaning the needle move when the engine is running, but when accelerating the needle moves slowly to the new RPM if at all.
The car in question is an 85, 300DS. I'm trying to put a trouble shooting process together, but I can find the schematic in the FSM to know what the components are that make up the tach system, nor do I know where it's sensors, or what sensors are used. Any help would be appreciated. Thanks

Greg