97 sport 4.0. Changed transmission. Now it won't run right.it starts ok and idles fine for about 2 minutes. Then it starts popping, missing and idleing very rough. If hold the accelerator down until it reaches 1500 rpms it jumps up and down from 2000 to as low as 100 rpms. HELP!!! Is it something with the transmission or could it be some sort of electrical issue. Changed the IAC, thought maybe that was it.