E83 n52 idle issue (lots of replaced parts)

[Winston24]

Iv been hunting this idle issue from day one. It's random hot or cold only at startup. It will surge if you shift directly into gear and it's not idling correctly. A quick rev always eliminates the problem. No hesitation issues. I think it got worse with new vanos solenoids... 🤷

Iv done the following. All oem or OE.
No codes or faults.
85k miles

Vanos solenoids
Vanos check valves
CCV/valve cover
Eccentric valve sensor
Spark plugs

Now I'm just throwing money at it. I'm going to smoke check for vacuum leaks and get the diagnostic program to work for future diagnostics.

Il keep throwing money at it but I need my next logical step.

ICV?
Dirty throttle body?
Various sensors (cam/crank)?
Vacuum leak? (I checked the oil cap...)

[MarcoZandrini]

What are you using to scan the engine computer (DME in BMWspeak)? Can you log and post long and short term fuel trims? It could be a vacuum leak but vacuum leaks don’t disappear with a quick blip of the throttle.

I think you’re going to have to have the DME scanned with BMW-specific and proprietary software. You can obtain and set up this software (INPA) on a laptop for under $50 which includes a special cable. Search the diagnostic software sub forum for threads on INPA. Also search the forum for threads on INPA in which Balidawg has commented. He’s the guru.

[Winston24]

I wasn't entirely convinced about it being vacuum because of that al,so. It runs absolutely perfect besides this random start issue and my vanos, check valves didn't have any buildup or very very little. Engine looks clean liqui moly 5w40 for the last 30k miles every 6 months (3-5k miles)

I have the brand new INPA installer ISTA+ (v4.27) ISTA-P (3.67) and a cable from bimmer diagnostics waiting to be installed on a fresh windows 10 instillation.

Il be sure to search for his threads!

[jclausen]

You could find a good independent bmw shop and have them take a look

[lexkaz]

check your gear first ... if no engine error.
you shift gear it is no idling correct right? and when you park idle stabilize?
if you have ista look at rail pressure and inlet pressure before and after throttle valve. this need to be about half of atmospheric pressure (before)

[Winston24]

When it randomly starts with a bad idle if you put it into drive or reverse before the idle stabilizes it might jerk you as the idle bounces (like 100rpms)

I have removed the fuel rail a couple times now but this issue was present randomly when I bought the car at 55k.

Ista is my next move.