[mictang]

Well, This has been some "fun" experience that I would like to share, comments and suggestions are welcome too.

So I have a Euro 325i, plastic cover N52B25 and MSV80, had a rough idle and difficulty starting in cold problem for some time, never properly diagnosed (I thought it was the fuel pump, a reputable shop suggested worn cam/eccentric shafts).

Recently started misfiring badly and turns out cylinder 6 failed compression test miserably with practically zero PSI and wet test was just under 75 PSI, figured it must be the rings and decided to swap to a 3 liter engine instead.

The engine was from a 2012 that's supposedly a new car which ended up being an insurance write-off. It is used but looks pristine under the valve cover and the pistons are shiny silver with a light layer of carbon build-up when looking through spark plug holes. Had the shop (who was also the supplier of the engine) replace the valve stem seals and various gaskets just for good measure, and swapped the engine over. Also the CATs were ruined during the misfire (bank 1 was glowing red, the catalysts were all wobbly when removed during engine swap) and were hollowed out as a semi-temporary measure.

The shop tested the car briefly and left it to idle for a couple of hours before I picked it up, but I soon discovered a serious oil consumption, the e-dipstick dropped 3 ticks (3/4 quart/L) in like 20km, and there is significant vacuum under the valve cover. The consumption rate slowed down to about 100km per 1/4L before valve cover was replaced with another used one, there is now only a slight vacuum like normal.

Thought the problem was solved, went home (drove another ~50km), and found the oil level has dropped another 1/4L, and there is still white smoke coming out of the exhaust on deceleration. Pulled the plugs and found heavy oil fouling on cylinder six, and noticeable black build-up and oil film on cylinder five. Did a warm compression test on the new engine and 1-4 was very consistent at around 170 PSI, 5 and 6 had visible wet oil shine on piston and are at 182 and 195 PSI, which I assume is due to oil presence.

I have read that the N52 PCV valves are closest to cylinder 5 and 6 on the intake manifold and looking at them I think so too, it was also said that cylinder 6 was the worst in being blasted by oil and thus most prone to fouling. I swapped spark plugs 1 and 6 and left the car to idle for ~ 20 minutes, and there is a visible film of oil on the "new" spark plug 6.

So I guess I could either run the car a little longer since perhaps there is just some more leftover oil in the manifold that coated spark plug 6 again, or the shop has suggested they can check the valve stem seals again, but I somehow doubt it, it is a fairly new engine and they did replace the seals.

Alternatively, I could also replace the valve cover with a genuine OEMo one and replace the tubing too, but I find it a little hard to justify given the vacuum in the valve cover is normal.

That about sums it up on the mechanical side of things so far, and I'll update when I have more news. Comments and suggestions are welcome.


As for coding, I tried the method here using bimmerlab 328i file but couldn't get it to work, getting checksum, conversion, and consistency errors from the command line. Already contacted bimmerlab as well as StageFP waiting for reply, I would be happy with either a stock 330i map that's free or relatively cheap, or an actual tune.

The car does drive somewhat badly without a proper tune, with hesitations in certain rpms and near red line, but normal driving was ok and it does have much better torque than before.

[NZE90]

You can test the PCV diaphram with a mightyvac (hand vacuum pump with gauge) there is a vacuum vent pipe on top of the PCV valve. Just apply vacuum to that pipe and watch the gauge to see if it holds. That will confim 100% if it's ok or not.

[mictang]

Originally Posted by NZE90

You can test the PCV diaphram with a mightyvac (hand vacuum pump with gauge) there is a vacuum vent pipe on top of the PCV valve. Just apply vacuum to that pipe and watch the gauge to see if it holds. That will confim 100% if it's ok or not.

I didn't test it with a gauge, but did try to blow air into it and it does hold. Funny thing is, the first valve cover had a new aftermarket diaphragm on it but still pulls a strong vacuum in the valve cover. So I am doubting the reliability of used covers right now, but on the other hand, the vacuum is quite normal right now on the second valve cover, behaving just like other N52 cars in the shop which I compared to.

[mictang]

UPDATE Feb 19:
Replaced both DISA flaps, one of them had worn seals, cylinder 5 is now dry and free of oil. cylinder 6 is the same with heavy oil fouling.
took the car for a drive and there is noticeable smoke upon deceleration (engine brake then idle/rev on natural) and it goes through oil fast.
shop offered to re-do the valve stem seals on them, will know more come tomorrow, but I have an uneasy feeling that it also could be the valve guides as I have read on the internet.

[mictang]

UPDATE:

Checked the valve stem seals, nothing noticeably wrong, checked piston #6 and valve guides to be sure, no visible issue either.

Replaced valve stem seals again and put in new valve cover, car has been driven over 1000 km with no oil consumption.

something interesting: car kept reporting 2A39 valvetronic learned limits outside tolerance, tried several motors and relearned a bunch of times, even took off valve cover again to visually inspect the eccentric shaft.

tried the 323i to 325i to 330i method using 328i RSA delete from bimmerlabs, one Canadian 325 VIN happened to work and flashed RSA delete and 328i to 330i map. 2A39 gone! So if anyone runs into similar problem, valvetronic values are different between the N52B25 and N52B30!

Car seems to run full 330i power, but has DMTL and region mismatch error (2FA3) due to the bimmerlab file being US spec, probably doesn't affect anything but is an eye sore, planning on getting a full custom tune.