93 DelSol Si auto.
I've always had a manual trans so I know nothing about automatics...but It seemed like it couldn't decide which gear to go to. It would kinda just float between gears. But 2 seconds later figure it out and be fine. The other day it did that but would go back into gear. I was driving normally about 40mph and it just wouldn't go in to gear. After I turned it off then on it worked for a few miles and did it again. And in my driveway it sits now.... also my speedo doesn't work

Is my problem the ECU? From what I've read from various places on the net, that could be the problem.

P.s. I've already changed the VSS.

 

It could be, but it can also be clogging valve bodies inside the transmission.

You could try and do a 3x3x100. By that I mean the drain 3 liters, fill 3 liters, drive 100 kilometers, drain another 3 liters, fill 3 liters, drive another 100 kilometers and then drain 3 liters for the 3rd time, fill with 3 liters and call it a day.

That could potentially help clean out some of the tranny, it can also move the gunk to other areas. It could be too late for your tranny or it just may need a decent servicing which I just described.

 

For some reason, there's no mention of ATF fluid level, ATF changes, CEL codes, or throttle cable adjustment.