WiTilt : 1 or 2% of strange measures

I’m working on a car application using accelerometer.

WiTilt is configured at 15 Hz and +/- 4g.

I monitor accelerations returned by the witilt in a car running at normal speeds (my application is for track use but I’m doing tests at low speed).

X accelerations are OK (no strange values), but I have 1 or 2% of Y and Z accelerationw which are not good (values from 700 to more than 900 !!! that means 2 to 4 g ! Impossible in a car for lateral acceleration for example). WiTilt is fixed on the armreste of the car.

Of course I can eliminate theses wrong value by program but is it a malfunction of my WiTilt ? can WiTilt be used in car ?

Other question : in +/-4g mode, can I assume a variation of 100 for X,Y,Z = 1g ? I can’t see anything about range values for X,Y,Z and g values in the manual.

Thank you for your answers (and sorry for my english).