Loud Idle/Acceleration + Tire Cupping Questions

[sxhaller]

I recently purchased a '00 T4R SR5 with 205k miles on it (one owner, most service records, clean condition). Except for a minor cupping on the tires and a small oil leak, the truck is good condition. I was previously told by American Tire Co that the cupping on the tires was minor and would fix itself with on time rotations. Other than a rough ride (have Goodyear Wrangler Authority), I haven't had any issues with loss of grip or bad handling... until yesterday when we had rain.

I was fine driving on the freeway around 70mph but once I got off and made a small turn (not speeding), I loss control and drove left into the plants in the middle divider and swerved right across two lanes before obtaining control. My only guess is i had some water and with the cupping, lost control. The truck was driving fine except I noticed that when I accelerated, I started getting a whinny, almost chainsaw type of sound. I am now noticing it every time I hit the gas and the more I push it, the louder it gets. I also noticed that during idle, the RPH fluctuates from 600-1100. The higher the RPH, the better "grr" I hear, but when it goes around 900, it sounds like a chainsaw idling.

Any suggestions on what this may be?

Also, is the minor cupping (per the tire guy) an issue enough where I should replace them? Before this, I have never heard of tire cupping.

Thanks in advance.

 

[topless87]

On a rear wheel drive vehicle the front will cup out like that and the rear will wear flat. You can either replace them or just deal with the 2 cupping out some. With rotating them it will eventually fix itself but could become noisy slight roar. But the tires cupping should have not made you slide or lose control.

 

[kball]

So the noise started after you hit the plants? I'd check everything out under the hood and under the truck.

 

[topless87]

Sounds like a vaccum line may be busted or leaking some