Ford Repair Questions? Ask a Mechanic for Answers ASAP
Hello, do you have a test light or volt meter to do some testing. if you have a weak glow plug relay or glow plugs you can have this concern. It sound like it is the issue since it doesn't do it if you plug in the vehicle.
You want to test the glow plug relay for internal resistance not the voltage drop the battery has. if the glow plug relay has more than .3v voltage drop it will cause hard starting and rough running until it warms up. If that is ok then you could have injector o rings that need to be replaced.