Hi all,
I have a slightly modified 1970 Mach 1 and now have issues with something electrical. When it is running, if I open the door, the interior lights come on and the engine stumbles and stalls some times. If I am in the car and start it and have it running if I turn on the parking lights, same thing it stumbles and sometimes stalls..turn on the head lights, same thing.
runs smooth until lights of some kind come on then rpm drop and engine stumbles??
help! No idea where to start..as I hate electrical

thanks