XC70 2001 with rough idle but otherwise works great

[shodanx]

Hello,
Last month the car was in my garage and I tried to diagnose the issue again.

When the car arrived I made a first video of it after driving about one hour on the highway.
On the highway it works great, trouble only arises when you get to stop signs and parking. Only when idle or close to it.

So first video, you can see the idle is kind of too low, sometime it's stable sometimes it's not
Giving it little shot of the gas pedal will make the rpm fall low enough that the low oil pressure warning light up

first video

Around 4:16 I touch what I think is the evap cannister shutoff valve ? but I'm not sure this is it.

About an hour later, I made a second video, this time the idle issue is more pronounced
I believe this is after we have tried swapping the coils from a known good xc70.
It didn't improve things, we put them back. The behavior shown in this video is more typical of the car when it's having bad moment, the car is hot at this point.

second video

You can hear the car misfiring and not idling right, I'm giving it gas many times, it's not super clean when I am giving it gas or not

Third video, we connected VIDA and did ERASE ALL
Car no longer misfires ?!???? Idle is great !? (mostly) What is going on.... Bad sensor ? bad calibration ?

RPM still takes a dive when I let go of the throttle but it's much better behaved.

It seems there might be two separate problems, something causing misfires and something else causing RPM drop on throttle release

There was a third factor making the car even worse, seized AC compressor that made restarts a nightmare, but we pulled the relay on that and it fixed it.

third video

After third video, we went out for a second 10km ride see if maybe we've fixed it. We also found a tube not connected to anything so we plugged it (one of three small hoses that I think are related to turbo wastegate control)

After the ride, the car is back to doing misfires, something changed in the computer...

fourth video

Went out for another ride, still having bad idle and misfires on fifth video
We tried something, don't remember what but it didn't help anything

fifth video

I have changed the spark plugs last year (it was doing the trouble before and after) I also changed the coils for all new ones, didn't seem to have made any difference either

I also tried swapping the mass air flow sensor with one from a known good car, it made no difference

At the end of the day, we did one last video, at first the engine has unstable idle and misfires
We do the erase all procedure and as soon as it is complete, it holds rpm steady and the misfires go away again !?

This video is not yet uploaded I am uploading it on youtube right now

[abscate]

Smoke test it and look for induction leaks

Test fuel pressure at rail with a gauge.

[shodanx]

Yes, smoke test is the next step, I am waiting for the US border to reopen as my new smoke tester is in a warehouse on the other side
(this one

As for fuel pressure, I didn't think that could be it since the car runs perfect on the highway (?) but it seems easy enough to check so I will next time the car gets here