[mictang]

Originally Posted by Jros

i could think about a cam bolt loosing torque and/or reluctor wheel losing position on intake side?

I don't know, if it is not electronic or hydraulic related i can only think about something mechanical being off, and thinking about the HVA job maybe it could be possible something was not torqued right or has lost the correct torque somehow, putting play in the mechanism.

the problem is that for checking this the valve cover must come off, so it would be better to check timing and intake cam bearing ledges (upper and lower) and to be sure change the bolts securing the vanos to the cams (one use torque + degree) at the same time...big job and not sure it would help

i don't think the software side can be at fault being and oem map.

swapping intake and exhaust cam position sensors changes nothing? if it does then the sensor now on intake side could be at fault

If it were the sensors wouldn't setpoint values change in attempts to correct it? The fluctuation only happens in intake actual values.

There were no immediate faults after the HVA job so I don't think they outright had an installation error.

It is not an unreasonable assumption that something lost torque, while I did have the large vanos to camshaft bolts replaced, they can be a possibility.

I had been thinking about what you suggested, with the addition of vanos actuator, if all of the other things do not show any obvious issue, then the only thing I can think of is the actuator.

[Jros]

sensors may be a long shot, I know, but swapping position to try and exclude them takes so little effort that i would do it just cause to be honest

[mictang]

Originally Posted by Jros

sensors may be a long shot, I know, but swapping position to try and exclude them takes so little effort that i would do it just cause to be honest

Swapped the cam sensors and there is no change, as expected. Cleaned sensor and solenoid plugs while I was there.

But, found some additional information, from a complete cold start, vanos was actually acting normal, but as soon as car reaches operating temp/oil pressure drops to a steady 2 bars (I left the gauge attached yesterday), fluctuations start to appear.

And from my street driving log, the fluctuations are still there at higher rpms/oil pressure, so this is somehow temperature dependent? I guess the springs inside the actuator could be losing tension at higher temp?

[Jros]

harness acting up when hot? would be interesting looking at vanos pwm signal with an oscilloscope vs logged

if not electrical then it would be mechanical tolerance related, and you could be right in thinking the actuator itself is at fault

in any case this is a pain in the @ss unfortunately

[WheelNut2]

Hey Mictang,

I checked my Vanos set and actual angles and they seems to track each other quite nicely. I didn't log them, but looking at the number in INPA with the car in the driveway it seems like they are quite close. I did find a 1.5* difference at 3000rpm on the exhaust side, but I'm not sure that would be a problem.

My Valvetronic adaptation was quite high though. Maybe something is awry there.

[mictang]

Originally Posted by WheelNut2

Hey Mictang,

I checked my Vanos set and actual angles and they seems to track each other quite nicely. I didn't log them, but looking at the number in INPA with the car in the driveway it seems like they are quite close. I did find a 1.5* difference at 3000rpm on the exhaust side, but I'm not sure that would be a problem.

My Valvetronic adaptation was quite high though. Maybe something is awry there.

I believe the Valvetronic value you are referring to is just the learned limit (something like that) and the max is ~179 so it sounds normal to me. My INPA never worked for the VVT page so I was using TestO or ISTA, but nonetheless normal range is like 20+ to 179 degrees.

Your VANOS values seem fine too, 1.5 is a really small difference.

I am planning to open up the VC and check the VANOS actuator/bolt/timing again. Hopefully, it is as "simple" as a defective part...

(Also did another cold start log and this time the fluctuation was there right from the start, so the steady VANOS values from last time was a fluke, making it look more like an intermittent pressure issue with VANOS)



In your case, I can think of two things to try, one is to intentionally trigger a VANOS/Valvetronic code, I usually unplug a VANOS solenoid or ESS sensor, you could also unplug Valvtronic motor and manually set it to different angles
(turn the hex screw on the motor and verify the angle in INPA). If your idle smoothes out, then at least you know it's one of three things: VANOS, Valvetronic, and CAT/O2 sensors (Valvetronic code causes a +30% short fuel trim but eventually evens out), I know I don't have the last as I replaced all O2 sensors.

The other is actually a software update, looks like you have a 2006 MSV70 car, so it is worth checking. My research on this issue has found a small percentage of idle issues being resolved with software updates.

Bimmerlab usually offer stock tunes according to your vin (for free) and they do not require any special procedure to flash. Check your current ZB in INPA (read UIF or something, plenty of guides available online) and see if there is a new calibration (0da) available for your firmware version (0pa), then simply follow Bimmerlab instructions to flash using the ready-made batch file and WinKFP. Calibration flash only takes about 1 minute.

You could also flash to the latest firmware (if there is one) and then flash the corresponding calibration, but firmware flash takes more time (~12 minutes) and is technically riskier.

[Mrmigs2011]

Do the n52 have rectarings on the cams like the n54, early released models had a steel ring that cut groves into the cam casing (forgot all my terminology tonight sorry lol) that causes the vanos to loose oil pressure in the n54, it was later released with teflon seals which corrected the issues in most cases, with your references so high I'm curious if they share the same cam and vanos design!

Also vanos pulse trigger wheels would be worth a look, with 8 degree swings I do think that would be enough to give rough idle performance. (Or stumbles rather)

[mictang]

Originally Posted by Mrmigs2011

Do the n52 have rectarings on the cams like the n54, early released models had a steel ring that cut groves into the cam casing (forgot all my terminology tonight sorry lol) that causes the vanos to loose oil pressure in the n54, it was later released with teflon seals which corrected the issues in most cases, with your references so high I'm curious if they share the same cam and vanos design!

Also vanos pulse trigger wheels would be worth a look, with 8 degree swings I do think that would be enough to give rough idle performance. (Or stumbles rather)

If it were the cam bearing ledges, it would only have happened in the last ~3 months/8000 km (I looked at the ledges back in May when replacing the valve lifters), which would be pretty unlikely, my oil still looks quite clean. And if I read it correctly, the date code on the VANOS units was 2010, so it was a pretty late production.

Pulse wheels can be a possibility I guess, as if the car was changing things like lamada in response to a VANOS fluctuation that wasn't actually there?

Hopefully I'll get the chance to check things again in the next week or so and will report back.

[mictang]

dug up some old photos from the last couple of months, now I feel a little stupid.

although they weren't loose from before, it looks like my vanos bolts are the affected ones after all, the bolts in the photo look silver (vs. the updated ones being black) and vanos date code looks like year 2010 (affected range was 2009-2011).

my cylinder head casting number was 7588273.03, if this is of any importance.

Guess I'll be just replacing them and see how things goes...

[mictang]

So I opened up the valve cover today, was planning on replacing the vanos bolts, but it turned out I had the older metal cam bearing seals (more on this below). The Vanos bolts are actually all correctly seated, and by turning the large Vanos bolt, only the camshaft moves slightly and not the Vanos unit, which according to my searches is indicative of working Vanos unit/tight torx bolts.

There are some wear on the ledges but according to BMW service bulletin, "If
deep groves are not apparent, the camshaft bearing ledge is acceptable and should not be replaced."

Note on the third pic, there is a similar level of wear on the larger camshaft bearing surface, so I am thinking just replacing the seals and bolts and see if things improve. I don't have timing tools so I will have to take it back to the shop.

Any inputs? At this point I am having some serious self-doubt about what the actual problem is, and if seals and bolts doesn't do it, head replacement would really suck.

[Jros]

if you have to pay a shop for a re timing job, you should consider adding new upper ledges and maybe teflon rectangrings while you are here. I know lower ledge will have wear too, but maybe a new upper would suffice in restoring functionality. That, and maybe trying ticket oil like 0W50 if you could find it, just to try and compensate for wear / grooving there.

Failing all this, i am afraid a new head (or good reman) may be the solution...that would suck

[Saico]

I don't think you can replace upper ledges only.

[tylerhart_21]

I am having a similar problem, but it’s the rpm’s jumping up and down (sounds like a big cam) at idle/off the gas. It has thrown the 2A82 code, and I have cleaned the vanos solenoids and the check values yesterday. Going to look at the oil cap but it looks like from the post it maybe the vanos itself. I will try to get a video of it doing it. Let me know if y’all have any ideas on how to fix it.

[mictang]

Originally Posted by Jros

if you have to pay a shop for a re timing job, you should consider adding new upper ledges and maybe teflon rectangrings while you are here. I know lower ledge will have wear too, but maybe a new upper would suffice in restoring functionality. That, and maybe trying ticket oil like 0W50 if you could find it, just to try and compensate for wear / grooving there.

Failing all this, i am afraid a new head (or good reman) may be the solution...that would suck

Thanks for the advice, actually I did have the rings replaced a couple days ago, I didn't pay labor since the engine came from the shop.


The intake upper as you could see had very little wear, lower was in a very similar condition. Exhaust side on the other hand, was much worse after opening things up again. It has a very typical deep grooving, but strangely, had teflon rings on the camshaft (maybe someone tried to fix it before, who knows).

The shop exchanged me a set of used exhaust ledges, that had a shallower groove, put everything back together, and the result was actually slightly worse idle.

Live data looks like there is a marginal improvement on the intake side, the sawtooth is at a lower interval (streatched out), suggesting a slightly better seal on that side. Exhaust now looks like what my intake did before.

In my area, a used head is around twice the cost of a new pair of exhaust ledges, but generally in unknown history and can be rather hit or miss. Ideally I would like to find a good head and just have good ledges on both sides, but if I can't find a good source for the head, I wonder if I should try a new set of exhaust ledges...

[mictang]

Originally Posted by tylerhart_21

I am having a similar problem, but it’s the rpm’s jumping up and down (sounds like a big cam) at idle/off the gas. It has thrown the 2A82 code, and I have cleaned the vanos solenoids and the check values yesterday. Going to look at the oil cap but it looks like from the post it maybe the vanos itself. I will try to get a video of it doing it. Let me know if y’all have any ideas on how to fix it.

Jumping idle is a typical VANOS symptom, I didn't have it before (It was a relatively low amplitude rough idle) but I do now.

If you have already ruled out all the other things, including vacuum leak and typical misfire items, open the valve cover to check VANOS sprocket itself (turn the large bolt in front to check for play and oil leaking jizzing noise) and the torx 45 bolts on the back (backed out/missing heads), if they are the culprit then you would be relatively lucky since they are not difficult to fix.

(I was advised by a local mechanic to try a smoke test from oil pressure switch port, but in my case VANOS area showed no leak, smoke was only coming out of cylinders 3-5 lifter area. But for bad cases of bearing ledge issue, this could be worth a shot)

If not, you can check the intake upper bearing ledge like I did, just remove two torx screws, no other parts need to come off. If they are worn you are likely going to need a new head.

And if none of these are the problem, there is a possibility only your exhaust side bearing ledge is worn, there are cases indicated in the BMW technical bulletin, but to replace them you will have to re-do timing which can be rather involved (still much better than having to replace the head).

[Saico]

mictang thanks for showing this datalog and registering those fluctuations. Seems that whis might be a good method to assess bearing ledges condition without physically looking at them.

Curious if anyone could remanufacture these ledges, seems like a normal job for an experienced machine shop. Unless they are coated with alusil or something.

[mictang]

Originally Posted by Saico

mictang thanks for showing this datalog and registering those fluctuations. Seems that whis might be a good method to assess bearing ledges condition without physically looking at them.

Curious if anyone could remanufacture these ledges, seems like a normal job for an experienced machine shop. Unless they are coated with alusil or something.

I also took a look at my other 2012 F1x 5 series with the same engine, it idles perfectly with a fluctuation within 1 degree on the intake side and 0 on the exhaust side (stock tune is -115, resting position). So yeah I'd say this is a good indicator for VANOS issue.

The head looks like a solid piece of cast aluminium with no special coating, I suppose it is possible to repair.




My local market has reman heads slightly more expensive than a good used one, so I am going with used.

So far I have found one that's good condition with casting number 758827101 and dated 2009 (on the back side of the extruding piece between cylinder 3 and 4, near O2 sensor cable clip), casting number is located in the same vicinity.

But both my current swapped engine and F1x are casting number 758827303 and dated 2012. I am trying to decide whether to go with the 2009 head or keep searching for a newer one.



There is very limited info on cylinder head casting numbers on the internet, but both casting numbers above are listed as improved for the valve lifter TSB, there do not seem to be additional revisions regarding VANOS bolts or seals. The TSB issued on 2014 regarding cam bearing ledge did not specify an end date range so I am guessing anything up to 2014 can have the metal seals, which is pretty much every N52 that exists (N52 ended production globally in 2015).

(Also in lifter TSB, BMW lists 7588273.XX as N52B30 and 7588271.XX as N52B30K. Yet I thought all plastic valve cover N52s were N52K?)

[mictang]

Thought I'd give a final update for anyone coming across this in the future:

Replaced the head with one that's the same casting number and dated 2012, there is a shallow groove on the intake side, just enough to catch a fingernail, exhaust side is perfect, camshafts came stock with nylon rings.

There are occasional fluctuations in VANOS readings but warm idle at most times seems fine now, intake tracks within 1 degree against target.

Idle is smooth (not as perfect as stock but likely due to headers and tune) and roughness readings among cylinders are close to one another.

It's been ~1500 KMs since and haven't had any code or symptoms, so looks like it's solved.