Originally Posted by shadoquad

If you disengage the clutch and give it some gas, and the revs increase while the response and speedometer have a significant delay, your clutch is not grabbing properly. Not to be confused with throttle lag. If your throttle lags, then when you put your foot down, there will be some lag before the engine revs. That's normal in a drive-by-wire car.

I've replaced a slipping clutch. The symptoms are quite noticeable. They go "release clutch, give gas, hear a vroom, wait a few seconds, car starts going".