Hi,
Can you post pictures of your project with the sensors connected and mounted in the car please?
Can you post a proper circuit diagram, showing ALL your connections to sensors and batteries?
Label the connections to your components.
The circuit you supplied did not show any needed information.
Have you got any bypass capacitors on the motor and have you checked your wiring.
Electrical noise from the motor can easily get into the sensor circuitry.
Have you kept the motor power wires away from the sensors and their wiring?
Can you post links to spec/data of your sensors, are they just the IC, or are they mounted on a breakout board.
Both sensors work with 3.3V, but if mounted on breakout PCBs there may be a voltage regulator included.
Tom... 