[M-Simon]

Hi Guys,

 
I need your advice please, after more than 1 year of diagnosis and part-changes of my F13 N63 Engine (408 HP Version -new engine in 2016 current km= 100.000).
 
The engine is starting to slightly shudder when it is hot and in higher gears with low RPM.
-No problems when the engine is cold
-No problems when the engine is in sport mode

 
I have already exchanged so many parts without success, that I am feeling (I am!) an idiot!
 
-Coils
-Spark plugs
-Air mass sensors
-Lambda Probe before Catalytic converters
-Lambda Probe after Catalytic converters
-No fault codes in ISTA
-No errors with ABL misfire detection
-No engine leaks
-New Torque converter
-Injector Cyl. 8
-Emission test on both banks
-Timing Chain is ok
-New Crankshaft Position Sensor
-New Vanos Solenoids

 
The smooth-running values in idle are bad (from my point of view for all injectors, but the car does not shudder until it is hot and driven in high gears with low rpm and only just a little acceleration.
Do you have any idea what I can do next?
 
Thanks a lot for your help!

[____ANGEL___]

Do a compression test, imho cylinders 3 4 5 7 are bad.

[M-Simon]

Thank you, which values do you have rated? Minimum, Maximum or Average?
Do you think that the engine has an internal damage?

[____ANGEL___]

All three.

I think cyl 3 4 5 7 have losses in compression, i suggest a complete rework but first of all check compression.

[Node]

So many part cannons, and not a single elementary compression test done... Which should be THE FIRST when you see that much variance in cylinders...

[M-Simon]

As I said I have botched this. now I have ordered a compression tester and will make the test.
The reason, why I have not made a compression test was that the engine runs in all other conditions with great power and without further problems.

[Node]

Also ABSOLUTELY no info what has changed after you replaced that injector. That could also move scales for compression vs injectors.

[____ANGEL___]

So many part cannons, and not a single elementary compression test done... Which should be THE FIRST when you see that much variance in cylinders...

Yeah, i try to explain this in simple words.... in an high pressure fuel system when an injector compensate too positive respect others, the more possible cause is a loss of compression, this happens because there is more space with less pressure to fill so automatically the injector with the same energy inject more volume.

[M-Simon]

But the values are NOT fuel compensation. They are related to the engine smoothness in microseconds. That means a value with a minus means, that the cylinder is not contributing for the engine movement.

[____ANGEL___]

Yes stocastical test, that indicates the same thing.

You wrote:
No misfire
8 injectors changed
Sparks changed
Coils changed

But some cylinders still not contributing, so what stills there??? Only compression.... Did you ever checked also for carbon build up into intake? But this has to be really a lot to do this defect. Anyway do a compression test and post the results