Driving fine, then suddenly losing ability to speed up

[Tyrannosaurus]

2009 Aveo5 roughly 70k miles.


Hello,
My mechanic is stumped. My next step after this is paying the local Chevrolet dealer just to troubleshoot it for us.


My car sounds perfect for about an hour or so, then it gets loud (my mechanic leaves it on in the shop). When I was driving it, it'd drive completely fine on my work commute (about 30 miles). I had a check engine light come on, called OnStar, they gave code P0171. My mechanic, however, is getting P0011.


It will suddenly stop speeding up. I normally start in 2nd gear as 1st is so touchy. It started where I couldn't quite get enough gas to start in 2nd so I dropped down to 1st. Within a few blocks (stop signs every 1-2 blocks), it'll get to where I step on the gas down to the floor and nothing happens at all. The car will sound like it's off but it's not. Occasionally if I keep it like that, it'll suddenly rev the rpms for a second, then nothing. If I turn it off for a bit, I can start it again and it runs fine for a while again. It did run really low on oil at one point.


At one point before giving up, I could only speed up in 4th gear. If I got it to 60mph (highway speed for getting home), I could maintain the speed in 5th gear. However, if I dropped speed at all, I could not speed up again. At that point I let it sit on the highway overnight, then drove it 50 minutes or so to my mechanic without any trouble whatsoever.


My mechanic says my car is possessed and he's never seen this before, lol.


Please someone tell me you've encountered this and have a potential fix! I'd really love to avoid paying just for diagnostics. I'm injured and broke right now.