Help: problem with GTA V6 Turbo

Just wondering if anyone has encountered a long term fault i have had with a GTA Turbo, its a awkward one to explain, but hear goes.
If the car is left for say more then a week it will start up fine, but after about 10 mins runing it will start to falter "trying to stall and reluctant to rev on the throttle" somtimes it will try to rev on its own? Whilst the cars playing up like this if i push on to keep it running it wont improve, Switch off and go back the next day all will be fine and stay that way if not left more then 3 days, If left more then three days or so its back to the begining again? Just wondering if anyone has encountered anything like the above?
Just to add, Its my dads car, he's owned it for about 8 years, low milage, 45000 genuine mls, Good cond, its been parked at my house for about 7 of those years, started up every month or so, (even with the above prob) I am tempted to buy it But? ill post another topic later
Thanks
Steve

Sounds like a fueling or electrical/fueling problem. When you start the car and its in warm mode, it runs rich (as on 'choke'). If the CO potentiometer level has been set to low, once its warmed up, it will be running very lean, maybe too lean, and this can be the cause of it trying to stall. It revving up again is just the idle speed control valve trying to stop the vehicle stalling, but there isnt enough fuel to rev, so it drops revs again....and around you go in a viscious circle.

It could be dropping an injector through a faulty plug, but Ive found the Alpines will still idle stabily running on 5 or 4 cylinders.

It can be faulty sensors, ie coolant temp or air temp. If any of these are disconnected or there is a break in the wiring, it will run lean on warm up and not idle and struggle to rev. I disconnected these two sensors this morning on my car, and it is a pig to start, and it does throttle up and down as you say.

Not trying to plug, but it would be worth hiring my diagnostic unit, as this will tell you if you have any sensor faults.

If there is a split in the Map sensor pipe, this will cause a fault too..

Other than that it could be fuel pump / fuel filter....check all the basics such as plugs, leads, cap rotor etc...

Thanks for the reply David, With the car not been mine i have been reluctant to really touch anything, but i did change the plugs and fitted some new KV85's neither of the above made a difference Ill see what happens re: buying etc what would your diagnostic unit pinpoint

You should do the cap and rotor, these cause more problems on the GTA than dodgy leads or plugs. The electrodes just corrode and get worse and worse if the car is just sitting there.

My diagnostic unit plugs into the diagnostic port and tells you all the reading of all the sensors, notifies short circuit or open circuits in sensor feeds, but cannot tell you anything mechanically related such as dodgy injectors, leads, fuel pump etc.,.