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BMW N62TU Smoking and hesitation diagnosis help with diagnosis

6446 Views 17 Replies 6 Participants Last post by  Psam550
Hi all,

Having some blue smoke and acceleration hesitation problems with my 550i N62TU. I expect the valve stem seals but am not 100% sure. I did some extensive diagnosis but need your help with this. Maybe things are interrelated or I have serveral issues. This is what I have done so far:

--- Vehicle ---
BMW E60 550i Euro
Model NW51
Engine N62TU
Gearbox ZF6HP26
Mileage: 175000km / 110000mls

--- Software state ---
GKE195 Gearbox ZUSB = 7592144 (latest?)
EK9286 DME ZUSB = 7593395

--- Symptoms ---
hesitation on low acceleration (1000-2000 rpm)
blue smoke when revving engine after 30+ seconds of idling with warm engine
oil in intake manifold
there are coming noticeably blow by gasses out of the valve covers when the CVV hoses are removed (as to be expected I guess)
sound (engine I guess) changes a bit after a long drive (2 hours+). Only noticeable when driving slow (<30 km/h). Vanos?
low engine torque at low RPM's (550-3000), but maybe that is just my perception
engine idling quite rough; cylinder 6 roughness value between 2.00 and 3.10
revving engine from idling not very smooth (also some minor hesitation)
drive train juddering during very low acceleration when the engine is cold (not sure if this is relevant)
slight drive train vibration during acceleration and coasting around 100-120 km/h
several small engine oil and coolant leaks
old coolant looks dark/greyish
no fault codes

-- Relevant checks/repairs ---
new crankcase ventilation valves (hoses are all clean, except some oil)
no vacuum leaks found with smoke test (exhaust not tested)
both engine oil dip stick tube and filler cap have suction
catalytic converters not clogged
fuel pressure during idling: 3.2 bar (nominal value is 3.5 bar)
compression on all cylinders ok
no DISA valve/sleeve movement when cycling ignition (according to the BMW documentation they should move. Can anyone confirm?)
intake manifold under pressure around 50 mbar (as it should be)
fuel trim see picture (+0.5 for additive is this percentage??? of ms?)
fuel system cleaner added (no influence noticed)
driving under high load (caravan in mountains) for two tanks (Shell V-power 100) also no influence noticed
new air intake filter
new engine oil+filter; Castrol Edge Titanium 0W-30 (BMW LL-04)
new spark plugs
coils swapped around cylinders
coolant changed
new battery

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1 - 18 of 18 Posts
Yep sounds like valve stem seals.Do you have excessive oil leaks?Leaking exhaust valve seals will cause extra pulses of positive crankcase pressure.BIG discussions on this subject.Threads go on for days.Search read.
Thanks for your reply Dolfan. I did read a lot the last couple of months. And was hoping I only had a CCV problem. After all the checks/repairs mentioned above I was/am suspecting the valve stem seals also. Strange thing is however that oil consumption is not abnormal (do not have an excessive oil leak either, only small ones) and that the fumes that are coming out of the valve covers (after removing the CCV hoses) do not contain oil, or at least not noticable when putting my hand with a white piece of paper in front of it. Can it be possible that the oil is coming from the intake valves and then straight to the intake manifold? I guess that would be quite unlikely.

Secondly could a valve stem leak leakage cause the hesitation during low acceleration, the rough ideling and the positive additive mixture values? Or are these symptoms totally unrelated? What would be the best way to check this?

This is a picture of the oil in the intake by the way:

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How high are your additive values.Should fault code if its too high.
The additive mixture values are around 0.5-1.0. But I do not know in which units this is given. Is it percentage or milliseconds? According to the usual BMW way of representing mixture values additive should be in ms and multiplicative should be in percentages. But INPA gives percentages for additive. See the image in my first post... This is rather strange don't you think? I do not get any error code. I have read somewhere that the mixture values would need to get very large to trigger a fault code.
OP: You're in good hands with Dolfan. Also, thanks for a very carefully thought out diagnostic post. Wish everyone did that.

There's a very experienced mechanic on here you will do valve seals in your driveway for 2500. Sorry, I'm not good with names. Check "valve seals" for his name. Has good references.
Thanks Banglenot for that.

I live in the Netherlands so shipping the car to the US would be costly. But thanks for the tip anyway!
Yes wlamer your post are excellent.The questions you ask have never really been definitively answered as they have been discussed in length.Trial and error leads most on this forum to agree valve stem seals as the cause.I know a couple of other members have fixed large oil leaks and did not change valve seals.These few cases curing the idle smoke issue.Oil leaks could be vacuum leaks thus CCVs not closing.Easy test for this ,pull cap on CCV and check to make sure its sucked down.

High crankcase pressure at higher RPMs with bad valve seals could be pushing oil to intake?Still the oil in your intake may not be whats burning at idle?Sorry for jumping around so much,my head is spinning now.LOL.
Thanks banglenot.My wife gets upset I'm on here too much!
That's a lot of oil in the intake - How much suction from your oil filler/dip stick while running? Your corrugated tubes (intake to valve covers) are in good shape with no cracks? Even though your CCVs are good, if you don't have a sealed crankcase, they won't work at all. Also, try disconnecting your Vanos solenoids as others have and SeaFoam for the carbon build up?
Hello A B,

There is a lot suction on the filler cap and dip stick. Under pressure is around 40-50 mbar in the intake when idling or under low acceleration. Under pressure goes away completely when accelerating harder (all according to INPA readings, sensor could be faulty of course). This is normal I assume since the throttle valve should open more in that case and let the valvetronic do the 'throttling' work. Maybe this explains why the engine is blowing out more blue smoke during idling?

I have to say that the idling behaviour does not differ much when I pull the dip stick or filler cap. One would expect rougher idling due to the added unmetered air, but I do not notice much of a difference.

I have smoked the crankcase/intake system with a smoke tester and found no leaks. Although there can be a small/difficult one to spot.

CCV tubes are in good shape, as are the o-ring seals. No cracks.

Why would disconnecting the Vanos solenoids help is this? This is a simple check and definitely worth a try. But I want to know what and why I am doing. Can you elaborate more on this?

Read your threads on several forums about the Seafoam, unfortunately we do not have access to that in the Netherlands due to import restrictions of chemicals. At least no one took the effort to make it happen.

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I had this handy - I'll try to find the other info;

Thanks for that info AB Able Truck. I have not tested disconnecting valvetronic because of the increased (and unintended) increase of intake manifold underpressure. First I try everyting I can before trying this.

I have set the minimal valvetronic lift to 0.8mm and increased the idling RPM to 600 (was 550). Idling is better (vibrations wise) and also the smoke seems to be less. Any clue why this is the case? Maybe it is just coincidence or related to enviromental conditions.

Any had some luck on this issue with flashing new DME software?
Increasing lift and idle speed moves the eccentric shaft to a more advanced position.Possible new spot on the shaft that hasn't been worn by bad intermediate levers.Lots of info and threads on this also.Vibrations at idle caused be uneven valve lift and cylinder fill.Unplug the Vanos system defaults to throttle plate.
Ok, but I meant the smoke. Why is the smoke less with increased valve lift? Only reason I can think of is that the movement of the intake valves is lager and therefore the seal works better somehow. Other than that I see no relation.
My opinion is that with exhaust valve stem seal failure, the ones that have pattern failure on N62 engines, that increasing internal vacuum in engine will decrease oil flow down valve stems past the hardened and enlarged seals.
When you increase lift or disable valvetronic the throttle is closed and inlet vacuum increases. Increased vacuum decreases crankcase vacuum with perfectly functioning CCVs.
Normally, with full VT function the lift to get correct idle sped may be .25 mm. When you increase lift then the throttle has to be used to control engine speed by closing throttle down to a minimal opening as with engines with no lift control method like VT. Disabling VT causes full throttle control for engine speed regulation.


The smoke is most likely the valve seals. The other issues sound like the tranny is acting up. I had the same issues. BMW installed a new tranny. It could also be the Mechatronics unit or valve body in the tranny. You can replace that by itself. Or, it could be the adaptive seals above the unit are failing. I found that driving in DS helped a lot! Good luck.

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