E70 35d - Rough Idle & Misfire - SOLVED!

[Algold415]

Hi all,

I got some issues with a 2010 X5 35D (w 150k Miles) that I can't seem to figure out. I got the car about a week ago, it was not running perfectly, but I hoped I can get it fixed if I pick it up. Been trying to run diagnostics for a week and still not too sure what's going on.

SYMPTOMS:
When picked up the car, it was not idling very good, seemed like it was running on 5 cylinders. The interesting thing is that when driving on the freeway and applying more throttle, it felt like it was driving a lot better. As soon as I would let go of the throttle, it would have a stutter or shake, like it was misfiring.

CODES FROM 1st SCAN (same day after purchasing the car, ignition on, engine not on):
-459C (not present) - 459C Smooth running controller, cylinder 1
-4595 (not present) - 4595 Smooth running controller, cylinder 6
-4596 (not present) - 4596 Smooth running controller, cylinder 3
-459B (not present) - 459B Smooth running controller, cylinder 5
-4CE1 (not present) - DDE: Misfire detection, cylinder 1
-4679 (not present) - 4679 Fuel injection rate monitoring
-492C (not present) - DDE: Reducing-agent active tank temperature sensor
-4BAC (present) - DDE: Reducing-agent active tank fill-level sensor signal
-447B (not present) - DDE: Oxygen sensor

CODES FROM 2nd SCAN: (cleared the original codes, turned on the engine, got these after a couple of minutes)
-4BAC (present) - DDE: Reducing-agent active tank fill-level sensor signal
-459C (present) - 459C Smooth running controller, cylinder 1
-4CE1 (present) - DDE: Misfire detection, cylinder 1
-4596 (not present) - 4596 Smooth running controller, cylinder 3
-492C (present) DDE: Reducing-agent active-tank temperature sensor

I read a bunch of posts about the injector replacement (mostly due to water getting in from cracked cowling and corroding injectors 5 & 6), CBU, and injector harness having shorts or broken wires resulting in one of the injectors working intermittently. I understand that I also have codes for the DFP/DEF which I'm planning to address later. Right now, just trying to make the engine run smooth so I can start driving the car normally.

WHAT I DID SO FAR:

INJECTORS:
1. Tested injectors for resistance & ground short (between pins 1 & 2).
-Injectors 1,2,3,4,6 all showed 181.7 kOhm on the multi-meter, all went up to that resistance virtually the same way (tool showed 15kohm, 160kohm, finally stayed at 181.7).
-Injector 5 showed 180.7 (it seemed to not be as stable when finally reaching 180.7, it would jump over 181.4 and go back to 180.4, but then sort of settle around 180.7)

2. Tested all injectors for ground short, found none (would hold one end of the multi-meter on injector metal body, and touch each of the 2 pins)

INJECTOR WIRE HARNESS:
1. Took apart the junction box under the cowling and disconnected the end of the injector wiring harness, then checked each wire by color (12 total wires) - found all wires to have continuity.

2. Tested each pin of the injector wire harness for ground short, found none

INTAKE MANIFOLD:
-Upon examining the intake manifold, it seems that there is quite a bit of carbon build up (on the ports and the flaps). I moved the rod that moves all flaps and the same time and all 6 seems to be operating good. My next step is to clean the manifold and the throttle body and see if that makes the engine run smoother.

QUESTIONS:

1. Did I do the injector test correctly? I don't have any software I can use, so hoping that the multi-meter test should suffice.

2. Although the injector wiring hardness didn't show any breaks in the wires or shorts with the ground, is it possible when the wire can be loose or shorted during engine operation when vibrating?

3. Is CBU a common issue for misfires, and am I understanding the following correctly? Looking at the carbon build up it kind-of makes sense, when the flaps are mostly closed at idle or low throttle, the carbon buildup on the flaps might block the airflow. As I throttle up, the flaps open and hence the carbon buildup no longer blocks airflow and has much less effect on the mixture. It kind of explains that when I throttle up, the car seems to get it's power back and drives better.

NEXT STEP:
-I'm planning to do the CBU cleaning, but if that doesn't fix the issue, I don't know what to address next. Please let me know if you have any idea of what else I can check.

Thanks!