Unknown Issue - help! - Audi A3 Petrol 2012

[tuba]

Bought a 2012 A3 Petrol end of Jan, and at the end of Feb car wasn't turning on. Long crank and then doesn't turn on. Car works fine for short journeys but seems like when the car runs for longer than 25/30 mins and I turn it off, it won't turn back on for another few hours. Three times the car stopped working mid-journey. It loses speed and eventually stalls and turns off. 

Changed coolant temp sensor, crankshaft sensor, throttle body but none of these are fixing the issue. The computer diagnostic system says the below but despite changing the throttle body, these errors are still coming up 

• Throttle control unit malfunction
• Throttle actuator electrical & mechanical fault

Could possibly be a fuel issue? How do I diagnose this without changing yet another part without being sure. I've been working with my dad and his mechanic friend on this but nothing is working. 

Edited March 19 by tuba

[Steve Q]

Could it be a cam sensor? 

[tuba]

Is this the same as crankshaft sensor? If so, we've already tried changing this

[Stevey Y]

52 minutes ago, tuba said:

Is this the same as crankshaft sensor? If so, we've already tried changing this

Hi no camshaft sensors are different but from your faults and seeing as you have changed the the throttle body I would be looking at the throttle position sensor on the pedal.

Steve.