Guages Get Crazy Under Load
 

Alright guys, I am getting tired of this issue and I'm stumped. I recently put together a turbo kit for my '90. Whenever I get above 50mph or so and give it gas or get into high load in 3rd, 4th, or 5th gear; my tach, oil pressure, and water temp gauges go all willy nilly and it doesn't feel like it's pulling to it's full potential. 1st and 2nd gear gauges work just fine and pulls hard. I suspected a grounding problem but I cannot find the source and I'm getting flustered so I am asking for help.

Here is the issue on film. You should watch it one or so times for each gauge.

A little background info:
'90 stock motor 1.6
Tuned on a DIY Megasquirt 3X I built myself

Here are the known grounds that I was told to check.
The two behind the fuel rail
https://www.miataturbo.net/attachmen...ine=1384107483

The engine head to firewall ground. I actually replaced this one so see if it made a difference. I also have an extra Megasquirt ground and my AEM wideband grounded here at the firewall as well.
https://www.miataturbo.net/attachmen...ine=1384107483

I relocated the grounds under the brake boost to here.
https://www.miataturbo.net/attachmen...ine=1384107483

I have checked the PPF ground and it is fine and intact. I am out of ideas.

Here is my build thread for those interested

Here is my Megasquirt build thread for those interested

Can you take a wire wheel or sandpaper to each of those locations (both on the connector and on the chassis)? They look pretty dirty/corroded.

Also, check the clamps/connections on the battery itself. Sometimes they can get corrosion or work their way loose. Take some baking soda + water to clean it up, then sand paper/wire clean it as well.

I will try that. I was told to ad a ground somewhere from a honda guy. Would that be a good idea?

How are your motor mounts?
I remember reading about a guys motor moving on the mounts and causing MS resets.. Long shot.

It couldnt hurt to add a temp ground to help in the diag. Run a wire from the battery to engine. 10ga or bigger. Just run it through the car and through the firewall if its easy or just around the door. Just to see if it helps at the different locations. A clean ground is a happy ground fo sho.

I put in brand new mazdaspeed motor mounts and engine lift plates in spring, but how exactly would that happen out of curiosity? I may try that if I can source the wire. Thanks for the help!

I took your advice and gave the few engines grounds a good baking soda/water paste bath and wire brush scrubbing. Do these grounds at the battery look like they need some work?
https://www.miataturbo.net/attachmen...ine=1384920489

And here is my ground up under the footwell that Bill mentioned. It seemed to be tightened by Zues and I couldn't get it off, but it looks secure, a little rusty though.
https://www.miataturbo.net/attachmen...ine=1384920489

I plan on adding a 10gauge wire from the battery to the motor to see if that does anything. But I have to wait until I get my cold start/WUE settings right before I can do much. Having trouble starting and already fouled out plugs.