E46 318i N42B cold start rattle/idle.... (not the timing chain)

[g-man hl]

I replaced the timing chain recently it fixed the slight shudder when idling and light rattle during cold start.... so it's not that.

This time a similar noise is back but worse along with a rough idle.
During cold start it hangs at a very rough 1.1k revs, but the moment I tap the accelerator with my foot it's gone and stays gone.
Idling revs drop down to a smooth 750 where it should be and no more issues.

The car wasn't in use much the past 2 years, sometimes not used for weeks at a time. This is due to lockdown and a new job where I walk to work. 156 000 kms on the clock.

My theory:
From reading forums I gather it is an oil / oil pressure or hydraulic issue.
Hydraulic meaning:
- Timing chain tensioner, which i think was changed
- The "cam... something something" needs to be bled.
- The vanos

I wonder if the "oil service" included in the recent timing chain job was just an oil change and they did not change the oil filter.
So I suspect my oil filter might be clogged because it wasn't changed.
Next oil service due in 3000km, last oil service was during timing chain job.
The cold oil only starts coming through it when oil pump pressure increases (when I tap the accelerator)
Apparently the oil pressure can be too low but still high enough the make the oil light go off.
That's my theory anyway.

I am buying a service kit tomorrow and doing an oil service, will update in the next couple of days after some more cold starts.

 

[g-man hl]

Update: Didn't happen next morning. got the service kit anyways. I think it's gone. but found a new problem when getting new tyres. i was under the lift and found an oil leak on the gearbox output shaft or selector input shaft. So today I cnc cut a press fit tool at work and bought a 30mm DEEP socket. the two critical things for that job. not connected to above issue lol.