If the car has no problems revving up when you step on the gas then you need to look at the transmission. From your original post it sounds like your car is spinning the flywheel but this power isn't getting to the transmission.
If you don't know what you're doing with transmissions, then bring it to a shop for an inspection. They can check your torque converter, this is where the engine's power is transferred to the transmission. It's possible the converter isn't engaging properly.
It could be something as simple as fluid/filter change or getting your bands adjusted. If you haven't kept up with your tranny fluid/filter change schedule then it'll probably blow soon after you replace these items.
|