[gclions]

Guys,

Car is still missing something, so I pulled more logs today. I hadn't spent much time looking at my knock sensor graphs because they always looked pretty comparable between the eight of them, and trying to look at all eight at once causes my BT software to crash.

Well, I decided to look at them one bank at a time. Ended up with some screwy results on cylinders 6 and 7. 6 seems mostly fine, though it is a little higher than 5 and 8, but 7 is really high. It looks like the car is cutting timing as a result, but it isn't bad enough to throw a CEL. So I either have some serious knock/pinging on cylinder 7, or for some reason that sensor thinks I do.

Have any of you replaced a knock sensor on the N63 before? If not, any other BMW platforms? I'm still feeling a loss of power, it will build boost but it just isn't as quick. The car feels heavy and slower than normal.

My thoughts are to:

1 - inspect the spark plug
2 - swap coils between cylinders 5 and 7
3 - swap plugs between 5 and 7

Then check my logs again. If that doesn't fix it, or if cylinder 7 is still an issue specifically, then I am going to try to check the tightness of the 8mm bolt holding the cylinder 7-8 knock sensor in place. If loose, torque it down and check to see if the problem is clear. If it is tight, then I plan to swap the knock sensor for 5-6 with the one for 7-8. Check it again.

My concern is gaining access to the sensors, as they are up underneath the intake manifolds, bolted to the block. Pretty much by where the oil pan bolts to the block. Has anyone pulled all of the underbody panels off enough to get access to the bottom of the engine?



I'll post a DIY video if I end up swapping sensors.

Thanks in advance,
Grant

[gclions]

Want to put some data here as a place holder as I work through this issue. Below are voltages generated by the knock sensors at idle (750 RPM), 2000 RPM, and 3000 RPM.

I have swapped spark plugs and ignition coils between cylinders 5 and 7. I didn't see much difference, so I swapped coil 5 for a spare coil I had from previous efforts. It's condition is unclear, but I didn't see much change on cylinder 5. I have one more spare to swap, so I'm going to change out the coil on cylinder 7 which seems to be the worst by far.

Cylinder 1: 0.37/0.49/0.51
Cylinder 2: 0.58/0.67/0.87
Cylinder 3: 0.37/0.60/0.70
Cylinder 4: 0.40/0.60/0.76
Cylinder 5: 0.55/0.62/0.89
Cylinder 6: 0.46/0.58/0.72
Cylinder 7: 0.52/0.72/1.16
Cylinder 8: 0.36/0.64/0.77

More to follow.

**Update

I swapped the spare coil for coil 7, same numbers. So I swapped coils 6 and 7, same numbers for each, so I can rule out the coil as the source of my problem.

So I'm still of the mind the knock sensor could be loose or failing, though 7 and 8 share the same sensor and 8 doesn't look terrible.

Any ideas?