Wierd Electrical Issue

[Grommish]

Working on a 05 Mazda 3i 2.0L, and when rolling to a stop, the tach sometimes starts going nuts, bottoming out, etc and the car will stall. Putting it in Neutral seems to keep this from happening. This has all the classic signs of a electrical issue/alt issue, but the alt is throwing out 14.3v @ idle and this does NOT happen if the car is just sitting there (as in, not in gear).

Suggestions on where to start trying to trace this issue? Any help would be greatly appreciated!

 

[djltoronto]

Working on a 05 Mazda 3i 2.0L, and when rolling to a stop, the tach sometimes starts going nuts, bottoming out, etc and the car will stall. Putting it in Neutral seems to keep this from happening. This has all the classic signs of a electrical issue/alt issue, but the alt is throwing out 14.3v @ idle and this does NOT happen if the car is just sitting there (as in, not in gear).

Suggestions on where to start trying to trace this issue? Any help would be greatly appreciated!

If the tach starts acting weird, and bottoms out - and at the same time the engine stalls.... It sounds like the tach is reporting accurately!

 

[Grommish]

It bounces, bottoms, recovered, bounces, and then the engine dies.. Only was happening when the engine was under load (in gear, brake on).

I yanked the negative terminal and stepped on the brake and let it sit for a few mins.. hooked it back up and it seems to be running normal again.. Very very odd..

After I posted, I went back outside to dicker with it while I still had some daylight.. I was initially leaning towards an electrical issue, but I seemed to rule that out.. The "only in-gear" thing was making me think Tq Converter (Since its an ATX). Is the Stall rate PCM Controlled in the Mazda's? (I've got Ford's and Honda's and none of them are ATX, so I'm just shooting in the dark on that one). Could resetting the PCM have affected it?