My 2008 Scion tC is all stock and I'm trying to figure out "why" when I'm accelerating uphill "mostly" does the steering wheel get loose and slightly sway left to right under accelerating?

Any ideas?

 

What is torque steer?
I think that's your answer.

 

Why would a stock vehicle have torque steer?

 

i believe that the tc is rated with higher torque than horsepower...plus its front wheel drive.

 

well, no one designs torque steer in mind, it's usually the fault of the suspension engineers. When you make over 300hp in a front wheel drive car, and you don't have a limited slip differential (where both front tires get traction instead of one) then you'll have torque steer. But lower hp like the tC, 160hp, it can be designed not to have torque steer. Cheap front wheel drive cars from the late 80's had it because of a bad suspension design/set up.

now with that said, the tC DOES NOT have torque steer! The ONLY time that I found that there was something LIKE torque steer was when there were ruts in the pavement and the low profile tC tires were following them. that's back when I had pirelli's, yuck! those things would tramline (following the grooves) on anything. It would wander all over the place, almost like following an unruly child.. lol.. was way too much work to keep correcting the steering wheel.. I switched to Toyo and never had that issue again, was much more enjoyable to not have to keep constantly correcting the direction of the car..

so.. it could be your tires, what do you have on there? If it's pirelli, then i'm not surprised it's doing this. let us know what you have..