Something odd is happening with idle RPM. It seems hesitant. Sometimes the engine vibrates quite a lot. Once it stopped at the red light. Idle RPM seems to vary, sometimes I’ve seen it as low as 400 RPM (if I can trust the gauge), but usually seems at or just below 600.
Strangely, vibrations disappear when it’s at 400 RPM. It vibrates mostly when it’s close to 600 RPM.
No issues whatsoever when I step on the gas and the car starts moving.
What can I do?
Probably unrelated, but I thought it’s worth mentioning: there was a lot of corrosion on the battery cables due to acid leaking, and I had to re-crimp the negative cable recently. The battery issues appear to be fixed for now. I don’t think I knocked something out of whack while fixing the battery, but the idle vibrations started soon after that. Maybe it’s just a coincidence.