Update - this morning, with the engine completely cold, it wouldn't start properly (with the old sensor). It would idle slowly for a few seconds before cutting out, and the accelerator did nothing. I put the new sensor in again and it started fine first time. But the temp gauge is wonky again - it's in the middle of the scale with the engine almost cold. Is it just a case of recalibrating the gauge to work with the new sensor or something like that? Or does the sensor have 2 separate functions (one for the engine management, one for the temp gauge) and the old sensor is working on the temp