The car is a 94 z28 with an automatic. The previous owner put on bbk headers and flowmaster muffler. I just bought the car. I did check it out and had a mechanic look at it but now the car jerks around when in reverse or drive. In park its fine. The rpms jumps between 700 and 1200 and the car lurches even when im on the break. No check engine light. The engin also gets real hot fast when the rpm is jumping around. It may be happening only when the engin is warm, like halfway on the gauge. I may be imagining that. Please dont tell me its the transmission.

 

actually it does jump around when i park i was mistaken

 

Do a search on opti-spark issues.