Citroenxara Fair

I have a Citroen Xara 1600Gasolina of the 2ooo and has slightly uploaded

The idle speed is controlled by the fuel injection computer, based on the information it receives. If you have a malfunctioning sensor, it can cause this problem. For example, the engine temperature sensor, the power steering pressure sensor, the air conditioning pressure sensor, etc. One easy thing you can do is clean the idle air control valve (IAC) with contact cleaner.
It's a black device located on the throttle body.

If the check engine light isn't on, it's unlikely a sensor is faulty. You can clean the intake manifold and idle air control valve with Duco thinner or some electrical degreaser and see how it goes.

The malfunction indicator light isn't on, so we can rule out a sensor issue. Also, the diagnostic tool isn't showing any faults, and the strange thing is that the idle is only slightly elevated to around 1000 RPM. It could be the idle air control valve, but I don't have the means to check it and I wouldn't want to replace it without being sure

If you have access to a good scanner, I suggest you go to parameter measurement and check the values ​​to see if they're consistent. For example, it's happened that right after starting the engine, the temperature sensor reads -134 degrees, which means everything is malfunctioning
, but the diagnostic light doesn't come on. There are several things that can cause the engine to run poorly without the light illuminating. Good luck.