Jerking and Idling Hard

[knm2011]

I have a 97 explorer XLT, when i hit around 40mph it starts jerking like it is out of gas, if i hit the gas to speed up it stops, then driving at a steady speed it will do more. If im in park or sitting at a red light and it is idling, it idles really hard. Any ideas on what it might be before i take to a mechanic and spend a ton of money?

 

[crazymind]

When was the last time you did a tune up? I would start there.