Car: 91 SE-R DET swap with jwt ecu.

Problem: When electrical accessories are on (headlights, or defroster, or fan...) car will stumble, idle will hunt and Techtom MDM injector reading goes from 2.4ms to 4.5+ms. Black smoke pours from tailpipe. When accessories are switched off it goes back to normal.

Car ran perfect for 8 months until this crap started one day.

Fixes tried:

New battery
Newused alt from JGY
battery cables/grounds checked
maf and wiring checked
Ignitor checked
Coil checked
Plugs changed
No ECU codes


Thanks for any and all help

I found that the yellow/red wire on the connector that plugs into the alternator had broken. It must control the output of the alternators voltage regulator. Car runs like a champ again.