I took the car to Infiniti dealer, they couldn't fix it. The problem doesn't light
the Idiot light, so I guess they don't know what to do. The cars engine will randomly start racing, like roaring, seems like it is in second gear. Happens when
I stop for any reason, than start. It may or may not go away until the next stop.
I believe it must be one of the sensors tied in with the throttle body somehow.
I just don't know, I am not a mechanic, the car has 94,000 thousand miles.
Otherwise runs great. It driving me nuts. I had the TPS and the one next to it replaced. That didn't help.

Can anyone help.
Thanks

When it happens, does your tachometer actually show the RPMs jumping way up?

If it's just a roaring sound without any RPM increase accompanying it, you might just be hearing the belt-driven fan when the fan clutch engages it.

I don't think it's that, it seems like it downshifted to second and the engine is
working hard because it's in second.
I will look into the fan clutch.
Thanks
The RPM dial shows the engine racing when you start the car.

can we start with the service history (detailed, please) on your transmission?

What year car is this?

So when the car is sitting at idle, it idles normally and good, but when you're going at higher speeds it basically randomly downshifts?