Ford Repair: 98 Ford Winstar, service engine soon light, battery cable

Question
I have 98 Ford Winstar Limited 3.8L. It run well at high speed, but it has a problem when driving at traffic or lower speed. After a slight breaking, I feel the engine surging and I hear the sound like the car running over something. If it happens many time because of traffic, the "service engine soon" light goes on, but the car still run. After I disconnecte the battery cable a while. the light goes off.
Please help me to understand this problem.
Thank you very much.

Answer
Hello Hong, !st you need to know what is causing the check engine lite to come on, you need to have a computer test performed to see what the codes are. Once you know that then you can understand what is causung your problem. Hope this helps Thanks Tony