Allion fuel consumption rough start

Sounds familiar. I had a similar problem with my Allion (it's an older model, though). The symptoms were almost identical - rough starts and the fuel gauge was definitely moving faster. Have you checked the throttle position sensor? That might be related to the engine idle issue too.

Throttle position sensor, huh? Where exactly is that located, and is it something I could potentially check myself, or am I better off just taking it to a mechanic?

I wouldn't recommend messing with it yourself unless you know what you're doing. For me, the issue was a defective accelerator pedal module causing the throttle valve to not work correctly. Best bet is to get it diagnosed by a professional. Cost me around 205€ to get it fixed.

Thanks for the tip! I'll take it to a workshop and mention the accelerator pedal module and throttle valve. Hopefully, it's the same issue and they can sort it out quickly. Appreciate the help!