I have a 92 Cavalier with a V6. Car runs great for the first 10 miles, then the problems start.
When I try to slow down, it shudders and grinds and I have to either drop it down to 2nd or 1st (automatic transmission), or put it into neutral. If I'm slowing for a stop such as a red light or stop sign, it stalls when it's in gear. It idles fine in neutral, but as soon as I put it into gear, it stalls. I have to very quickly drop it into 1st and hit the gas to get it moving. From that point, it's sluggish, shudders and wants to stall. If I park it for 24 hours, it's ok until I drive it about 10 miles.

Any suggestions?

 

By the way, previous suggestions were to replace map sensor and throttle positioning sensor. These have both been replaced, but no luck.

 

I had an old 89 GrandAm with a 3.0 v6 in it and it would do the same. eventually once it warmed up it would just shut off and would not restart until the engine cooled off again, then it would start fine until it warmed up again. After replaceing numerous parts, we found out it came to be the Crank Position Sensor. Once it heated up it would fail which caused the computer to shut the car down for whatever reason.