Hi,
Hopefulky someone else has experienced this in the past. My 2012 1.3d multijet panda 169 has an issue where every few days (becoming more frequent now) the accelerator pedal just stops working completely. When the engine is switched off for half an hour itll start working again. Upon switching off the engine when the fault occurs, it makes an unusual whirring sound.

Probably not related but the engine is hunting a lot of the time when idleing from 800-1200 revs plus white smoke from exhaust. Not nesecarily when starting up.

Any one got any ideas?

White smoke is low compression or a faulty injector that is not spraying fuel correctly. If the injector sprays intermittently you can get a hunting effect but it's not a certain diagnosis.

Black smoke is too much fuel for the amount of air in the cylinder. Usually a turn fault or blocked air cleaner.

Sulphur smelling smoke is engine oil which is likely to be the turbo shaft seals. Worn piston rings will (usually) burn the oil before it goes down the exhaust.

I think you have two separate problems.

As Dave McT says, an injector or compression issue is the likely cause of the white smoke. White smoke is usually a cold engine problem, as it is unburnt partially atomised fuel. Once warm it would normally change to black smoke as described above.

White smoke on startup is often the result of faulty glowplugs. But once warm, if the white smoke persists, its a different issue.

Throttle pedal may be the potentiometer. I think this is 'drive-by-wire' so the throttle is a potentiometer, (like the volume control on a radio). It jas two tracks, and the ECU compares them, to avoid faulty readings. If it is ignoring it completely it might be well worn and need replacing. Or it could be poor connections between pedal and ECU.

To properly diagnose this, it needs to be connected to some diagnostic tool. The Fiat dealer can do this, but expertise may vary, and communication to you of the readings and diagnosis may be vague, apart from their repair estimate.
An alternative is MultiECUscan (MES). do a search on these forums and learn about this wonderful software. It mimics the Fiat tool, but needs a PC and some cables. If you update your profile to show your location, there may be someone nearby with MES willing to help out.

MES can show throttle opening, so as the throttle is moved you can watch the readings and see if it is correct.