Car speed slows down and speeds up runs a little rough when speeding back up it does a jerk.

Hook up a scan tool and check for DTC'S - diagnostic trouble codes before you jump to any conclusions an start to just replace parts. If it is a VSS vehicle speed sensor issue would set a code and turn on the check engine light. Other things can cause this.

is their black smoke at the tail pipe if their is to much gas

you have clogged fuel injectors, take it to a dealership only! they are the only place that has the proper set up to clean them. My 89 Mustang GT had the exact same problem and ford service center cleaned them for $80 and it was 100% better never had another problem, sold the car at 276K miles and it still ran perfect with no drips or leaks, the tranny finally went out. Never use those cleaners sold at stores they do more harm than good! they will void your warranty also.

Don't know about the speed sensor, but your spark plugs and air filter could be a problem with the black smoke and rough running.

Did you did any tune up,fuel filter,air filter,coils.

Could be several things, a vac leak, dirty throttle body, or faulty idle air control valve.
The computer controls idle speed by how much air enters the throttle body thru the valve.
Usually a vac leak would speed up the engine unless it is causing the rough idle.

Take your car in to have your check engine light code read. Most car parts dealers will do this for free. A possibility is you speed sensor on your transmission is going out.

Check for vacuum leaks on all hoses underhood. Make sure all intake componets are intact and they are tight.

Is the check engine light on? If so, get to an auto parts store, they should pull the codes for free.

Sounds almost like a bad throttle position sensor. The computer uses the TPS to help know when to shift on this car if I remember right, and if the TPS is bad, it can cause that jerking. Along with the car dying when slowing down after driving. But check everything else out first. Including electrical connections.

you have to change the spark plugs

Had same problem: cutting out at low rpm, jerking, a huge clunk or shudder at higher speed (like transmission was going out), and rough idle. All these symptoms were intermittent.

CHECK THE FUEL FILTER!! Changed the fuel filter and thing runs fine!!

PS mine 2003 expedition has 105k