001 Mustang: I'm being blocked from seeing the photo - says I don't have enough privileges or some such. Anyway, I've connected a spare 4 AWG marine grade eye-eye battery cable from a bolt hole just below the head - similar to a hole for the alternator bolt or AC bracket and run it to a engine mount bolt (on the body side of the rubber!). See anything wrong with giving that a try? I think it should show if this is the problem, anyway, and if so I'll get a new cable that's specific for the task. Both of my manuals do not show this ground lead, but do talk about removing and replacing it without benefit of a photo.

 

looking at heater blower housing. 3:00 position. about 4 inches to the right. thats where factory ground strap screws into firewall. mediocre design at best. other end of about 10" strap bolts to rear of engine.

much better to do what you said. heavy ground strap from engine to bolt on the frame.

 

So simple. Ran a 4 AWG cable from the block to the chasis and all is well.
Thanks for the help.

 

your welcome
i like happy endings