Help! Marquis Jerking/Heating and then runs fine until it happens again

Driving down normally and suddenly the car jerks and looks like shuts down and 2 seconds later is back running normal.
its scary if it happens on the highway!
When this happens, Check Engine, TEMP light and LOW FUEL lights are on!
At this point the car is overheating and I also notice small variations in oil pressure.
So, I stop to cool down and then 5 minutes later back on the road and working fine.
Sometimes I keep driving or cruising in neutral and the car cools down and I continue driving until it happens again...it heats up and then cools down.

The problem used to start only if the car was floored but now Its getting worst and happens anytime.

Took it to a mechanic and he flushed the coolant + changed the temp valve. Took the car for a test and floored it and it worked fine! no hesitation..nada! :D

2 days later, I have the same problem except its WORST! :(

Please help.