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Discussion Starter #1 (Edited)
I’ll apologize now for the forthcoming wall of text.

The last post here that I had made dictates the beginning of my dilemma. It seems no one has read it, and I haven’t found much relevant to J-rad’s initial issue that wasn’t covered already. So I begin this new thread...

For clarification, the car in question is a stock ‘91 5spd.

Through chasing the wires (red/Black), I have found that one of the wires that is showing ground (when it shouldn’t) leads to the ECU - when looking at the small plug from the ECU side, it’s the first one on the right on the upper set. When I unplugged the harness from the ECU however, it stops grounding out, leading me to believe that the ECU might be bad.

Some late 80’s/early 90’s Japanese cars have an issue where the capacitors leak onto the board, a la 1g DSM.When I found the wire grounding through the ECU it got me thinking. DSM’s suffering from ECU failure tended to still run, just with drivability issues. After pulling the board out of the casing I noticed a small amount of white residue at C711. Again, similar to DSM ECUs with capacitor failure.

So I guess what I’m trying to say is “I think my ECU is bad. Has anyone ever heard of this with Miata ECUs?”

Edit: for more clarification, the wire leading to the ECU was showing constant ground in all conditions except “unplugged.”
 

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i had a problem with power draining, then batteries being over charged that it would swell. replaced battery, alternator, then found out it was the ECU. this was on a -91
 
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