hi, it happens only at 800 rpm, it's like "resonating".
P0172 have happened before.(3 months ago)
low mileage

It feels like Oil Trap problem,
though nlo pressure on oil dipstick hole, nor whistling (it is but very minor small whistling)

Do you think it's the oil breather box?

 

Or the Electronic Throttle Control needs cleaning. Your throttle body is "fly-by-wire" and sometimes needs cleaning to stop the idle hunting.

 

Which part of Electronic Throttle Control can be cleaned? Throttle Body, right? or should there be somewherr I can try also?

 

+ I wrote it in wrong way, sorry.
The idle RPM is steady, but whenever I pass by 800 RPM or rev it to 800, engine vibrates a lot.

 

Idle should be 750 so not a whole lot of revving need to reach 800.Not sure about the new body-style if you have similar engine support and cross member on the bottom but on mine the cross member is bent due to hitting something and now it touches the engine support frame.It does vibrate quite a lot on idle.Even make noise.Check under if you have a similar problem.If yes then pry the 2 apart and squeeze some hard rubber between.

 

Ok, check motor mounts then. The main mount on the pax side has been known to split in two. After enough time the rubber wears away and you start getting a metal on metal "thunk" while accelerating.

 

Okay, the mount looks okay from the top but who knows, I'll try that.
The strange thing has happened, though.

Yesterday morning I drove it out 'without' dipstick(by accident, yeah, was in hurry, forgot to turn it back on). and realized the problem, got dipstick back to the car and, it's normal now.

I repeat, it did indeed comeback.

no rough idle, no excessive vibration.
What I don't understand is could driving without dipstick really do any benifits to the car? I'm confused now.

Happy news anyway.

 

You don't want to cover a problem with another problem. If your problems are related to pressure out of the dipstick then have the oil trap replaced. It might even be covered under a recall. Some models and years had a recall.

 

Turns out to be another lucky day
it sounds and looks like motor mount on the PAX side
confirmed by dealer

thanks for your advice!