car is bucking jerking. on 1997 Chevrolet Malibu

car is bucking and jerking,it runs fine when you first drive it.after driving for about 1 half hour it will begain to buck and jerk.seems worse when start the car after driving.also when you pump brakes in park the car jerks.

1 answer 1 comment
Really need to check the codes in the computer and do a diagnostic as this could be so many things, including a ruptured Power Brake Booster. Any Check engine Light or Service engine Soon Lights on?

http://repairpal.com/check-engine-light
no there is no check engine or service engine soon lights on i think i have some type of vacum leak and was told that i may need a map sensor im not sure what is going on ive replaced so many different parts and still have no idea i dont think i can have diagnostics on it because there are no lights on