I have a diesel common-rail 1.5l engined car. Lately I am facing an issue where the RPM needle is bouncing in the tachometer when the car is idling. The normal idling RPM is around 820. When idling, I can see the RPM fluctuating between 800-1000 rpm. This fluctuation is more evident when the AC is switched on. I can even hear some loud thud coming from the engine bay (due to the AC compressor) just when I turn on the AC, and along with the sound, the RPMs fluctuates even more. Few points:
- Coolant is in the max level.
- The issue seems to be more evident if I turn on the lights as soon as I start the engine(cold start)
Can anyone help me out on this?