Speedometer spikes, then car stalls...

Hoping for some advise...I've got a '93, auto trans...odometer 85,000. While driving, the speedometer feathers (floats) at 15-20 mph, and I know I'm going faster. Then the needle spikes up to 50-60mph, the engine stalls, I coast over to the side, drop it in park, and it starts right up w/ no problem. Goes a bit, and then more of the same, and it's driving me nuts. It's happened about 9x in the past 2 weeks.
I've had my mechanic look at it. The car sat for 3 days hooked up to a scanner. Nothing comes up. The mechanic took the car for a drive on 4 occasions, and nothing! He doesn't know what's causing this. I dropped $233. after the 3rd day...and the follownig evening..it happened again.
Any, and all advise is welcome.

Clean the battery cables... other than that, I guess put it into neutral to restart, at least you don't have to stop completely :dunno:

What did you spend $233 on?

Sounds like an electrical problem. Need more clues here...

No further replies needed ....
I sold the car, and got a Sebring.
Thanks to all that did reply.

No further replies needed ....
I sold the car, and got a Sebring.
Thanks to all that did reply.oh o guess you`ll being heading to sebring forums before too long!

I sold the car

Cool! Hope you didn't have to pay too much to get it out...