2008 e83 X3 3.0si Issue(s) - Need some advice!

[mangoose]

I bought an '08 M-Sport in September and have been chipping away at some of the maintenance items. As far as I can tell I have replaced everything that needed it and still have a few strange symptoms.

What I have done/had done (ie. new parts - shouldn't be the issue anymore):
- VANOS Solenoids
- New electric water pump ($$ ouch)
- New expansion tank, thermostat & hose
- New belts & tensioners
- 2 New ignition coils (they were showing faults and i have 6 working now with no faults)
- New gaskets on Oil filter housing and oil cooler
- Transfer case oil change

Lastly, I did the manual reset of the transmission "learning system" or whatever and noticed SOME improvement, but I still have a few odd things happening.

Here are my symptoms:
1. At idle, I get an intermittent shaking while RPMs dip from ~700 down to ~600 then back up again. It is noticeable for my passengers, and feels like something is wrong - but no engine code or fault. The timing of the dips are different every time, but it happens ~60-80% of the time when I am stopped (at red lights, starting the car for the first time, etc.) - no RPM fluctuation whatsoever at any speeds >5mph. This seems to be more of an issue while in Drive vs in Park of Neutral.

Here is a video of the idle issue, I did this while not moving, changing from Park, Neutral, and Drive, but all while not moving. The RPM movement seems small on the video, but you can definitely feel it throughout the car. - I have since refilled the washer fluid and that indicator has gone away


2. Secondly, sometimes the throttle response is either extremely delayed or non-responsive entirely. This is only an issue when there is significant load on the engine - like going uphill and trying to downshift - the transmission refuses to downshift and the pedal just goes all the way to the floor with no response, then a few seconds later, it seems like the transmission catches up and downshifts pretty harshly. I try and avoid letting that happen, and when I detect no throttle response, I back off and try again - sometimes it cooperates and downshifts as directed.

3. Lastly my cruise control will sometimes shut off entirely. I will set the cruise control with feet off the pedals and it will disengage with no direction from me.

I am not getting any engine codes, and an independent shop near me said the next steps would be 3+ hrs of just investigating to find the issue, and they said if it drives now, they wouldn't recommend it until something happens.

I would prefer to be proactive about this kind of thing, so if anyone has had a similar experience, and has an idea of where to start I would be very grateful!

[jdauria]

Id throw this up on bimmerfest.com X3 section, a lot more traffic over there. Without being able to see the video (due to work blocking all that stuff), sounds like a vaccuum leak or fuel pump/filter issue? Just a shot in the dark, hopefully someone else can chime in. I remember when my E46 3-series rpm would bounce all around it was due to tear in the intake boot. Not sure if those newer engines have that or not.

[Sprouty88]

The eccentric shaft position sensor

[mangoose]

The eccentric shaft position sensor

Could this be all the issues or just one? and would I get a code for it?

[Johno]

Wild guess is the idle is a vacuum leak. A can of starting fluid or electronics cleaner sprayed around the intake etc. Will find it if that's the case.