this problem has my mechanic and i going:screwy:. I have a 1993 sho atx. which seems to "down-shift" when i hit a bump or a pot-hole ( i live in the bronx so it happens like every block). What i mean by "down-shifting" is that as soon as i hit the bump my RPM's shoot up about 300 -400 but the car will have a loss of power. Can you guys please help me out. it has had a recent tune-up, we changed the MAF. i'm just completly stumped on this and would really appreciate any help that i can get.

Certainly doesn't sound like downshifting to me. Sounds like something is loose or the torque converter is unlocking.

Does the engine sound change like one with the engines jumping up by that much, or are you just going off of the tachometer? You may have an ignition coil with a loose connection internally. That could cause the lack of power and play games with the tachometer.

-Rod

Check the crankshaft position sensor. My 91 SHO had similar symptoms, but progressed to the point where the car would die. It would restart after a while. Took a long time to diagnose...
Good luck!