2000 grand marquis, 152,000 miles. Whats happening is sort of weird that ive never exerienced this before but whats happening is the car will run fine and then all of a sudden out of the blue it will just misfire and litterally "chug" almost like driving a car with a blown head gasket and blowing black smoke.

But this is the part that confuses me, when it does this i turn the car off and start it right back up and its fine again. It will run great for a while and then all of a sudden this happens and its getting more and more frequent to the point of about every 10 minutes, but everytime if i turn the car off and start it right back up it goes back to normal.

Seeing how something is being reset when i restart it it leads me to believe that its some sort of sensor or some monitoring device on the engine, but i have no clue what to look at.

What i have done is changed all the plugs, and all 4 o2 sensors and recently just changed the intake manifold (was cracked).

Thanks