1. unplug icp and see if engines smooths out. if so change icp with know good one. also check for oil in connector when unplugged.. if it has oil it needs to be changed. buy from international not ford. or look on ebay. i ve been giving $100 for them there. ford list for over $300.
2. what type of scanner.
3. do you perform cylinder contribution test? results?
4. wiggle all the wiring connections. see if you get any change in idle. check harness going in under valve cover.
ive got a customers truck that has an rough idle issue. had an icp code, unplugged it truck idles alot better. i had an extra, new icp and changed it and problem still exsists. will pull one off of another running truck of mine tomorrow just to make sure i dont have "bad" new one. his truck cranks and idles good for about 10-15 seconds and starts to idle rough. this truck has no codes now, passed the buzz test but shows 3 cylinders on the contibution test. 1,7,8. im gonna check into the idm tomorrow and probably pull the valve covers just to make sure of the harness and connections. will put a set of the wedges in there while im there if every thing checks out ok. his truck clears up alot when it gets above 1000 rpm but still doesn,t run quite right.