Definition of quantal. 1  1 [Latin quanti how many, plural of quantus] : of, relating to, or having only two experimental alternatives (such as dead or alive, all or none) 2  2 [quantum] : of or relating to a quantum.
3. Engine movement. Another symptom of bad or failing engine mounts is an engine that moves in the engine bay. If the engine mounts are in good condition, they should be able to secure the engine firmly in the engine bay.
If the ECM has any issues, it may throw off the timing and fuel settings of the engine, which can negatively affect performance. A faulty ECM may cause the vehicle to experience a reduction in fuel efficiency, power, acceleration. 4. Car not starting. Another symptom of a bad or failing ECM is a vehicle that does not start or is difficult to start. If the ECM fails completely, it will leave the vehicle without engine management control, and will not start or run as a result.