Weird ecu/voltage issues.
 

Recently picked up a 1993 S14 silvia K and having some voltage issues. I had a Link ecu installed, as well as full bolt-ons and a fuel system, and everything was running fine till I drove it on some very bumpy roads. The car starts and idles perfectly fine. I have a BTI gauge installed and noticed that out of nowhere low voltage at idle and under load, it seems like the ecu is dropping voltage from 10.8v to 6.4v and restarting. If I am parked I can rev it freely with zero issues and if I baby it around my neighborhood I see zero issues. I did some testing with the key on and I have 12.3v at the battery but I'm only seeing 9.35v at the ecu/BTI gauge, and with the car running I have 14.3v at the battery and 10.8v at the ecu/BTI gauge, checking both pins 49/50 and 59/60. I have no voltage on the ground pins. I belive I've located the ecu relay behind the ecu on the passenger side(left kick panel) and seeing the same voltages on the black teaced with white wire that I believe goes to the ECU power pins in the ECU plug. I'm lost and would appreciate any help or guidance. Thank you all very much!!

1st pic is car is idle roughly 750-850rpm, 2nd is voltage measured at battery shortly afterwards. https://uploads.tapatalk-cdn.com/201...3aca8a2875.jpghttps://uploads.tapatalk-cdn.com/201...a4982a41cb.jpg

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My G was doing something similar. It ended up being a loose ground terminal at the battery. Worth a check.

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I did check that after scratching my head. Looked over as many grounds as I could see and all seem good. Thanks

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Yea, my first thought was grounds as well. My car had a fluctuating voltage problem and what fixed mine was adding 2 grounds. I always question batterys no matter what.

There is a reason why Toyota loves their grounds. You can never have too many grounds. Add a few and see what happens. It also sounds like a wiggle test is in order. Check all grounds and connectors. There could be a damaged wire somewhere causing high resistance. What about the battery? It is overcharging which can cause issues.

Have a great day,
jared