my check engin light is on an sometimes it idles at 1000rpm then other times 1500rpm.alos it would shut off when idle low... now my jeep has a 4.0l 6cyl a/t trans and its only shifting at 5000rpms and it only lets me shift twice so once i hit 5000rpm 2 times thats all the gears its givin me .i just got a transmission put it in and still doing the same thing . do you have any ideas thanks so much jon