A capacitive sensor for an ignition testing apparatus includes a substrate bearing a sensor metallization and a ground metallization, an output lead, a mounting device integrated with the substrate and configured to permit the substrate to be releasably mounted to an ignition coil housing, and a sensor displacement assembly integrated with the substrate and/or the mounting device. The sensor displacement assembly includes at least one member configured to move at least a portion of the sensor metallization in a first direction toward an ignition coil housing and/or a second direction away from an ignition coil housing and/or a third direction lateral to the ignition coil housing while the substrate is mounted on an ignition coil housing using the mounting device.