Zanetapos

So here's how it goes:

Turn key, car starts, runs, drives perfectly fine. Turn key off - radio turns off, car stays running, power windows still work, I can still drive as normal.

Troubleshooting: disconnecting the battery does nothing. Removing main relay does nothing. I can turn the engine off by stalling it, but the radiator fans are still running and the fuel pump is still humming - at this point I can disconnect the battery and the car is finally entirely "off". Jiggling the key does nothing. "Rattling"/jiggling the wiring loom around the ignition switch and ECU does nothing. Rechecked all grounds and wiring I've ever come close to touching. Replaced main relay.

If I re-connect the battery, even with the key out, the fans and fuel pump instantly start back up. SOMETIMES after sitting long enough, the car will turn on/off as it should but after about 10-15 minutes, the shutoff issue returns and stays until I let the car sit for a few weeks again. This began as being more intermittent and would go away for weeks at a time but now it's pretty much always happening.

Applicable mods (wiring I've touched): MS3 PnP, FM Boost Gauge, AEM UEGO AFM gauge + wideband sensor, tapped the window switch power wire for a mini gauge near the radio, Hard Dog roll bar (moved the harness to the side), FlowForce 640cc injectors (uses a simple pigtail adapter), FlowForce R8 COP kit (uses a simple adapter), FM Stage 1 fan kit.


I'm making this post while at work to get additional input as I read through the factory wiring manual. I went ahead and ordered a new ignition switch. I plan on removing/unplugging mine when I get home to see if that will kill the engine. I also plan on unplugging the fans to see if that kills the engine - I read some random miata forum post that suggested checking the fans/fan relay because they've seen a faulty fan draw (or generate...? lol) enough power that it someone kept the rest of the system powered. I did just recently have to upgrade to this fan kit because I discovered my OEM fan plug had shorted and melted itself - funnily enough, during the time the radiator fans were inoperable, I'm pretty sure the car was shutting down as it should (I got stuck at MATG with no radiator fan working and drove it home 3 hours with highway speeds keeping it cool). Any extra thoughts or theories?

Zanetapos

I performed further diagnostics tonight - pictured below you can see where I have checked off what will shut off the dash lights/main relay/fans and what will not do this. The check marked items, when removed, successfully killed power to the dash and presumably ECU (since this issue is keeping the car running). The items marked with an X has no effect and the car will continue to see power/stay running if pulled/removed.

I cracked the 80A Main fuse when removing a neighboring fuse. I've got to order one before continuing my troubleshooting. I'll do the next set of testing with the car running.

curly

iTrader: (25)

So you have a 3 plug ECU and front/rear o2 sensors, I'm guessing 95.5-00? Which year specifically? Looks like NB1.

Since the room fuse kills the car, I'm not surprised the BTN1 and main fuse kill the car, since they both power the room fuse. I would look at items connected to the room fuse that may be shorted out and holding power on that circuit even when shut off. Room fuse powers all of the "always on" circuits of the car, so ECU memory, obd2 plug, auto trans memory, power antenna, radio memory, interior lights, and supposedly instrument cluster, but I couldn't find that on the wiring diagrams.

Start with aftermarket wiring like widebands and gauges, unplug them one by one and see if it changes anything.

My guess is the room fuse (hot at all times), is some how jumped to the engine fuse, which cuts power to coils, and is only on in start/run positions.

Zanetapos

Yeah my apologies, it's a '99. I'll give a look through both gauges, my wideband, and fans. I doubt the fans are the culprit since they're so far away and it was plug and play.

I was on a similar train of thought where something "upstream" of the room fuse must be shorted to another wire that isn't normally always powered. I just have noooo idea what it would be since I genuinely did not touch much at all wiring wise. I exclusively use crimp connectors and then heat shrink them and give them a light wrap of electrical tape too. Super annoyed that I've been so thorough yet somehow managed to have something go haywire years down the road.