I'd search for a vacuum leak first. Visually check hose and I personally use a propane torch and spray around (unlit!) propane and look for an engine rpm change. Careful about fires.

You can also get a smoke machine for a good price on the internet for a by-the-book solution

 

What do you mean by "vacuum"? do you mean the intake manifold?

 

Yeah, a hard brake pedal is a symptom of a vacuum leak. Often around the booster check valve.

The 5.7 is sensitive to spark plugs, it likes fresh OEM parts. Cleaning is rarely effective.

A leaky PCV can cause these kinds of problems.

How many miles are on the engine? Hard/brittle vacuum lines can leak.

The AC compressor normally cycles on and off at idle.

 

I checked the PCV valve and I heard a ball moving inside, I'll try to push some pressure in the opposite direction tomorrow, I will also try to put some silicone around the booster valve.

Car has 106k miles, vacuum lines checked and are fine

as for the ac compressor, i don't think it could have any influence on this because the rpm fluctuations are not regular, they are spontaneous.

 

I will add that there are more strange things happening in the car, the ambient temperature in which the engine operates is around 158 which seems too high to me, despite this the coolant temperature is correct, the oil temperature sensor constantly shows -80 as if it was blocked, I tried to replace it with a new one but the ODB scanner showed the same value despite the replacement. This car is my nightmare, on hot days everything under the hood is hot that you can barely touch it, you can feel the heat coming out from under the car when you get out. I checked the temperature of the catalytic converters but it is normal. I don't know what is going on. I bought this car recently and it seems to me that the seller modified the ECU software to hide the faults, but to find out I have to upload the factory ECU settings

 

Which throttle PID are you graphing?

 

it only says "throttle position" apart from that I have one more parameter to choose from called "relative throttle position"

 

The AC compressor may be the source of the noise you mentioned, not the rough idle. The PCM increases throttle a little to compensate for the compressor load.

 

I've added screenshots of the RPMs. I want to emphasize that I'm not just looking for an explanation for the irregular engine operation; I'm trying to find the cause. Despite replacing 3 engine mounts, which I forgot to mention, the uneven operation is still very noticeable as strong vibrations in the cabin. The engine runs smoothly for a moment and then suddenly, bang! a drop, or bang! an increase. When I look at the passenger seat, I can see it shaking. I read somewhere that dirty oxygen sensors can affect engine vibrations – is that true?

 

First you need to replace the spark plugs with fresh OEM NKGs or Champions. What does the oil pressure look like, stable? Do you have ignition timing data? Do you have fuel ratio data?

 

 

I recorded all the parameters at idle speed, can someone smart take a look at it, can you read anything unusual from it?