VP V8 Idle Issues

[VNCalais3800]

Hi all,
I recently en-counted a issue with the idle on my VP V8 wagon, i have replaced the fuel filter, spark plugs, and spark plug leads (no difference after installing these parts).
The problem i have is the idle does not stay at idle, the revs drop down around 500rpm or so and then revs back up to its normal idle rpm. This happens every 10 seconds or so. It does sound kinda cool but if the revs go over roughly 2500rpm and i take my foot completely off the accelerator the car stalls.

Any help would be much appreciated.

[Teletran1]

No fault codes?
Check around for vacuum leaks, clean out throttle body and try resetting IAC solenoid for starters.
I had a funny hunting issue in my VN V8, was the MAP sensor playing silly buggers (no codes were displayed either..)
Pays to check the easy stuff first.

[VNCalais3800]

Cheers teletran1 ill go and short the aldl connection out and see what code the obd display's.
I forgot to add that when i start it, it is a bit chuggish for a a second or two.

[VNCalais3800]

Just checked that, it read out code 12. 1 Flash pause then 2 flash's