I have a '91 auto convertible that runs fine in neutral or park but barely runs and has no power when I put in in gear. The check engine light comes on as well but no code is determined when put on a diagnostic machine or scanner, not even at the Mazda dealer. If I shut the car off and restart it in park or neutral it again runs fine but repeats the problem when put in gear. Is the transmission controlled by solenoids or vaccum? I have done no mods and bought it from the original owner, a woman in ger 50s or 60s. I have, however, had the computer replaced at considerable expense but to no avail.

I have tried disconnecting the battery for quite a while and reconnecting it but no change other than the check engine light going off. Any ideas??

 

fluid level; check it as per the FSM/haynes manual

if that doesn't work, swap in a manual and 4.1 rear end