Cold Start, Reverse gear problem

First start and the engine runs sweet but as soon as I engage reverse, engine shudders, sometimes stalls, runs like complete arse. Warmed up its fine. No probs going forward from a cold start.

Whats going on!

Thanks.

Edit, Auto BA Flacon 4.0L

I had similar where revs would drop heaps but wouldnt stall. I cleaned throttle body and I think the Idle control sensor! Fish will be along soon. He knows his stuff. Mine runs sweet as now.

With the BA it seems as though you may have blocked OCV (variable cam timing controllers) controllers, or dirty throttle plate. Start with the throttle body clean. Take the intake pipe off, and using Throttle Body Cleaner, clean around areas you can reach with the stuff on a rag. DO NOT open the plate with your fingers. Use a pole on the accelerator pedal, and turn the key on to activate the electronic throttle, it will open some what, then clean the bore and plate as best as you can.
The VCT actuators: drive the car once warm and going, etc, quite hard in a lower gear, say even 1st or second, manual mode, up to higher revs, say 5500, then allow over run, don't change gear, repeat a few times, or go down a looong hill in a lower gear, with a few bursts of gas (well, petrol anyway!) here and there. This should "Self clean" the actuators, which can gum up, more so in cars that are used around town, colder running etc. This was more prevalent in the earlier BA's, then a factory reflash of the ECU was made to assist the self cleaning.
Hope this makes sense!!!
Fish.

There is a PCM Update that can be done at a Ford Dealer.

Also as mentioned, clean throttle body, IACV (Idle air control valve), and Reset the KAM (Can be done at Ford Dealer or otherwise disconnect battery and leave overnight)