Having been around cars for a long time, this has me stumped.
2005 Renault Megane Estate with 1.4 K4J engine. Approx 125 000 km. Engine is restless at idle. Revs are unstable and feels like misfiring.
Been checking diagnostic data from time to time, but nothing that would point to an issue. Sometimes I get P0638 and P2120, but very rarely. Has to be a cold and wet period with about a week without driving to get those codes to appear.
I took my small scanner and some photos of the live data when running at idle and fully warmed up: LINK
I believe the scanner window is 15 seconds long.
To me it looks like an ignition problem, but the coils seem fine (common issue on this engine and according to previous service info they have been all replaced 2x now) and spark plugs are fine. When cold it runs fine and when you raise the RPMs a little. Also, when under load, like cruising on the motorway with a trailer, small surges can be felt as if the engine is starving for fuel.
LTFT is also a little too high for my liking but the STFT looks fine. Not sure about the ignition timing, it goes all over the place. Both O2 sensors seem to be cycling normally, the second one is a little slow and "hangs" but the ECU does not flag it as a fault. MAP also reads normal and stable.
What else to check? I can post more data if needed.