Why does it make sense that the car runs better after it was parked a few days?

[harambeto]

Hi,

Usually my M50 has virtually no power if less than 2500 RPMs, is accelerating sluggish, is not too responsive and has high fuel consumption. If I let go off the throttle the whole car jerks forwards and backwards. I thought it is bushings somewhere but this jerk is not always present. My motor appears to be one of the first M50s with no vanos, knock sensors or O2 sensors. If I drive my car every day then this is the usual behaviour. However, if I park it for a couple of days and start it up I have good acceleration and responsiveness and no jerking. How does that even make sense? Why does it matter for a car whether it stayed for 3 days or it started the next day? Is there any particular sensor that might "take a break" after a couple days stay and work fine ?

[Hofmeister]

try cleaning the mat and checking for vacuum leaks

[harambeto]

try cleaning the mat and checking for vacuum leaks

I tried an used MAF and there was no difference. Regarding vacuum leaks, I think I do have one, but why would it cause so intermittent issues and not all the time?