So I've just done an engine swap and the idle of the car will idle as said in subject. When the car is driving along its fine but as soon as it's in nutral for a few seconds the idle will go back to changing and will occasionally stall. Once it has stalled I need to disconnect the battery for a few minutes to get it to start again.

I did swap the ecu and I haven't had it stall and need disconnecting yet. But I've only tested it once as ran out of daylight.

I've changed the idle control valve, map sensor and my only other thought is the wiring loom.

can the ECU see what gear position its in ( Inhibitor switch)
and also did you teach the ECU after disconection Ie, maximum engine load for 20 seconds, Highbeam, demistor, in drive. there is a procedure for it someware.

Now that I have changed the ECU and had a J3 chip placed in and put a new ICV on, if I have it connected it will continue to rev on its own but as soon as its disconnected it will run semi smoothly but stall as previously mentioned. I was wondering if it is the J3 chip needing to be re-adjusted or not.

I think the stalling is just the dizzy not being adjusted correctly, which is an easy fix. I would just like to know how to fix the revving constantly, when in neutral or in between changing gears.

did you clean the ECU/J3 connections correctly

I didnt do it myself, I had a ford place do it for me. I just asked them to figure out why the ecu was playing up and they put a J3 in.

Check for vaccum leaks and that the manifold gasket has sealed properly?,I know sounds too simple but doesn't take much of a leak to cause the problem.