I am pretty sure I have a loose ground. Just bought a 95 z28 six speed. It **** off three times on my way home after buying it. Three hour drive on turnpike and over mountains. I didn't lose power but engine cut off. It did it when I hit hard bumps each time. I think I have a loose ground but not sure where to look for them. I will admit I am not the best mechanic. I had the same year and model z28 before with a auto trans. I did manage to put headers on it but it took me a month total. Mostly due to the fact in the middle of the year they changed the ports and summit sent wrong part of year headers. So not the best but precentant lol. Anyway where are the grounds I should be looking for? The alternator is new and battery the guy said was new. I will have them tested but due to it shutting off only on hard bumps and always low volt reading close or in to red I think it is a ground wire. Any help would be appreciated, thank you =))

 

Scan it for codes. Problems with the grounds or connectors for the Opti, the ignition control module (ICM) would set codes whan the power is lost.

One of the main grounds is on the ICM bracket. Look in the picture to the right of the ICM, where there are several ground wires under the nut that holds the bracket.

Courtesy of Shoebox:

http://shbox.com/1/coil_loc.jpg

There is a PCM ground on the passenger side of the block:

Again, from Shoebox, his harness photo shows the PCM gournd (bottom center of photo) and others.

1995 Z28 A4 Engine Harness

Also check the battery connections for corrosion or being loose.