Electrical 1990 5.0 Mustang GT electrical issues

[Fair]

Hey guys, My 1990 Mustang is having electrical issues. It starts up and ides just fine, But whenever I go over a bumpy road or hit an ok sided bump the car dies. when I go over small ones, the rpm gauge starts dropping and bouncing back up and the lights in the dash dim. However, the headlights don't dim when the car dies. So something is loose.
I know its not fuel pressure because I have a gauge and its hold pressure and the fuel pump, as well as the tank, are new. I only happen if the car hits bumps.
Thanks again,
Fair

 

[jrichker]

Does the radio shut off momentarily, or do the windshield wipers pause, or does the A/C blower change speed? If so you have an ignition switch getting ready to fail.