I dont know what it is...

I have a 94 s-10 blazer,82,000 miles 4.3L Vortec, that worked fine, until about two months ago. At that time, the car would rev as I reached speeds of about 30mph then would cease at about 40. After this problem arose, my car started leaking coolant on my passenger side floorboard, which I found to be that my heating core was cracked, so I replaced it. Then, as I was driving it once again, it would suddenly die, everything would lock up, if i wasn't on the gas. Even in idle, after about two minutes it just cuts off. Can someone help me with the revving problem, and with the cutoff one.

When it quits you need to check for lose of spark or fuel pressure.
Post back what it is losing.

On 94 ign modules and pcm and dist pickup coil are some things to check.
Any codes or check engine lights?

I found out that its a bad O2 sensor..thanks for the help

I found out that its a bad O2 sensor..thanks for the help

You are welcome and thanks for posting back hoew it went.
Mind telling us how you found bad 02 sensor.