[mj_mj_mj]

Ok, this is a long one. This car is giving me hell. Have a donor car which I am moving parts from to try to locate the problem 
Car: 530d N57. 

Issue; "missfiring" cyl 3-4 smell of diesel rough running. 

Steps taken so far; 
6 new injectors (2 times)  - no difference
New engine ECU (2 times) - no difference
Old engine overhauled with new pistons, valves and so forth. Basically new engine. -no difference
Another working engine mounted for try - no difference
HPFP - no difference
Wiring harness injectors and engine and glow plugs - no difference
All fuel sensors - no difference
Airmass sensor - no difference
Gearbox -no difference
Fuel filter - no difference
Fuel pump low pressure - no difference
Fuel pump EKPS - no difference
Intake - no difference
Updated with ISTA - no difference
All values of sensors check ie temperature and air mass , nothing awry

Sound wize it sounds heavy knocking, almost as if trying to run it on start gas. 

I am 90% sure it is a fuel issue, if I unplug the low pressure sensor the car runs perfect, but in limp mode. 

Anyone have any idea?

[M-Simon]

Have you also exchanged the cylinder head? Had a similar problem with the former N47 engine of my wife. The culprit was defective threads from the glow plugs. The glow plugs were not deep enough in the engine and not tight. After the renewal / re-cutting of the threads everything was okay.

[mj_mj_mj]

Have you also exchanged the cylinder head? Had a similar problem with the former N47 engine of my wife. The culprit was defective threads from the glow plugs. The glow plugs were not deep enough in the engine and not tight. After the renewal / re-cutting of the threads everything was okay.

Reneved the entire engine actually but still the same issue... 
So in a way, yes.

[kuno24]

Have changed camshafts and hydraulic lifters?

[bellphegorus]

did you change the Rail or the rail pipes?

[mj_mj_mj]

did you change the Rail or the rail pipes?

Both pipes and rail are exchanged.

---

Lifters and camshaft exchanged.

[crazybm]

Sounds like fuel supply issue, fuel filter plugged? low press fuel pump not producing good pressure or good flow? Contaminated diesel?

[Mis]

Same issue in the N57 was bad compression - 2 rods were bent...

Cold engine smoking, fuel smell, misfire, with warm coolant is was running ok.

[Fatalix]

Are you 100% sure the quality of the diesel in the tank is good? Possibly it is full of condensation or water. How much fuel do you have in the fuel tank currently?

Nevermind, figured it wouldnt be that when runs good with pressure sensor off.

[ap90500]

Knocking sound -> too high rail pressure. Rail pressure sensor, volume control valve, rail pressure control valve, all three checked and good? Engine control unit software flashed to 100% stock (btld and all swfl’s with esys, not ista)?