2018 Q7 CREC 3.0T oil consumption issue SOLVED...N428 valve

[Flyboy02]

Fellas,
Just wanted to share my experience with my '18 Q7 consuming significiant oil. I purchased my Q7 used with 67,000 miles on it with no real issues except maybe some oil-covered spark plugs which were a sign of things to follow. I soon began to see that the vehicle was asking for a quart of oil every 1250-1800 miles or so. I didnt like that at all and began monitoring and doing all of the typical diligence like Blackstone oil sample analysis, engine flushes/CERATAC, a manual dipstick, looking for physical leaks/seals/gaskets etc and logging everything. When that didnt work I bit the bullet and had the very expensive PCV service done at 78,000 after seeing a VCDS code for the secondary air. Still, the car consumed oil at the same clip.

When the PCV fix did not change the consumption I went down the road that others on the Forum have about low tension cylinder rings and other theories about oil...thinking that the vehicle must not have been properly maintained by the PO, which led me to a leakdown test. I then had the oil level sendor replaced because I never believed it (who does, right?). I was now thinking that this car had issues with the cylinder tolerances I had a leakdown test done. At 95,000 miles my engine was very healthy- returning 12/10/8/5/8/10% leakdowns (by cylinder).

The engine ran fine and VCDS would return no codes related except one about the N428 getting an implausible signal or low voltage (soft code, no CEL, not always present) - and thats where i started to connect that maybe the problem was there. Initially, a prominent Northern Virginia Audi/VW shop told me they must be spurious; but, I was down to my last with this issue and considering offloading my Q7 when I finally decided to have the N428 valve replaced.

And that was it fellas - 4000 miles since the repair and I have not dropped any oil... at all. This absolutely resolved my oil consumption issue.

My forum reading about these units is that the N428, which regulates engine oil pressure, to provide low and high pressure at the appropriate times based on demand, temperature and load - as a safeguard - fails to the high pressure position. In essence, the valve was causing the oil to "blow-by" and burn through the cylinders and probably coating my cats with soot.

My warning to you all is the VAGCOM scans that I regularly did during this process didnt always show the N428 acting up. So, if you have these symptoms and even a single N428 code pops up (P164E), I would take a long look at this...its also a lot cheaper than a PCV fix.
I hope this helps anyone going down this rabbit hole, back to enjoying my Stage II single pulley.

[Txlifter]

Good stuff. Wife's car is in the shop for the 3rd time looking for an oil leak. Already some significant repairs done(under warranty) with no change in consumption. A simple fix would be much appreciated!

[cadguy77]

Thanks for sharing your experience. Bookmarked for future reference.

[nicholas_b90]

Very interesting - thanks for sharing, OP!

Owner of a 2017 Q7 3.0T that was acquired just shy of 2 years ago at 65k miles. Following my first oil change, I soon realized that the vehicle burnt through 1L of oil in about 1200 miles, and now I am at 74k miles and the range between oil top ups seems to be dropping - I am recording about 900-1000 miles nowadays. I think it is safe to say that the main culprit of oil consumption on this platform are clogged piston rings. I understand a B12 piston soak or BG EPR flush to be the only effective 'band-aid' solutions to free up the rings, which I plan do to in the springtime once the warmer weather returns. However, I would like to continue diagnosing my oil consumption issue until springtime...

Based on OP's trial & error process, does a healthy compression/leakdown test confirm that the rings are functioning as they should, or does it mainly detect burnt valves and/or scoured cylinder walls? I am wondering if it would be wise to just replace my N428 valve right away seeing as it is relatively inexpensive, or would it make any sense to get a compression test done beforehand? I am trying to avoid replacing the PVC valve, as it sounds like many have replaced it without any luck with respect to reducing/fixing their oil consumption.

I have scanned my car via VCDS many times since taking ownership, and have not come across any major codes (or misfires, etc.), let alone the relevant P164E code to make me believe the valve is acting up - does anyone know if there is a way to data log the oil pressure to confirm a faulty N428 valve that has failed into the high pressure position?

[JLAllroad]

In most cases the oil consumption is caused by the oil control rings and piston oil drains being clogged up with carbon, this does not affect the compression rings so compression testing is not a test for oil consumption.

As for the PCV its not if but when it will need to be replaced, and anything over [emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6][emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6][emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6][emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]]]]][emoji[emoji[emoji6]][emoji[emoji6]]]k is what I would consider “maintenance” if I was already pulling the SC for something else (water pump, thermostat, carbon cleaning, etc)


Sent from my iPhone using Audizine Forum

[snowboardgod]

Do you have a part Number by chance for the correct new sensor? I have this code too.

Although I’ve more or less resolved my oil consumption via liqui moly oil flushes and additives such as yamalube in the gas. I was saying maybe 1-2 quarts between 5k changes and now I’m using 1/2 a quart maybe.

It’s my understanding that this will not cause anything with oil consumption at all, but it’s cool to see maybe it helped you. Usually it’s carbon built up in the rings which is why the piston soaks work etc.


Sent from my iPhone using Tapatalk

[nicholas_b90]

In most cases the oil consumption is caused by the oil control rings and piston oil drains being clogged up with carbon, this does not affect the compression rings so compression testing is not a test for oil consumption.

As for the PCV its not if but when it will need to be replaced, and anything over [emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6][emoji[emoji6][emoji6]][emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]]]]][emoji[emoji[emoji6]][emoji[emoji6]]]k is what I would consider “maintenance” if I was already pulling the SC for something else (water pump, thermostat, carbon cleaning, etc)

Sent from my iPhone using Audizine Forum

Your post got all funky on us with many lines of strange number emojis - I quoted the first few lines above in case you don't see what I see? I'd love to get the complete message if ever you get the chance.

I've decided to not replace this valve seeing as I do not actively have the DTC code stored in my ECU - for this reason, it is safe to assume it is in good working order.

Following positive results of a borescope exam and leakdown/compression test done by my local indie mechanic, I will proceed straight to a thorough B12 piston soak job... Compression was 158-160psi across all cylinders, and there were no signs of scouring on the cylinder walls (good cross-hatch clearly visible, etc.), which was very encouraging to hear.

[nicholas_b90]

Do you have a part Number by chance for the correct new sensor? I have this code too.

Although I’ve more or less resolved my oil consumption via liqui moly oil flushes and additives such as yamalube in the gas. I was saying maybe 1-2 quarts between 5k changes and now I’m using 1/2 a quart maybe.

It’s my understanding that this will not cause anything with oil consumption at all, but it’s cool to see maybe it helped you. Usually it’s carbon built up in the rings which is why the piston soaks work etc.

Sent from my iPhone using Tapatalk

Refer to this thread over on Audiworld for the part number and DYI steps: https://www.audiworld.com/forums/q7-...valve-3077107/

I have also been reading about the benefits of running through a few tanks with Yamalube Ring Free Plus as an additive to help clean and dislodge the piston rings - I probably will do that just before I proceed to do a B12 piston soak come spring time.

Regarding this valve and associated oil consumption, wouldn't a dysfunctional valve that has gone into its failsafe mode calling for higher oil pressure 24/7, push more oil into the cylinders even at very low speeds/RPMs? This paired with stuck piston rings would accelerate oil consumption, no?

[snowboardgod]

Just bumping this to see if your results have stayed the same?? I am dropping my Q off next week for a list of items and have a new oil valve ready for them to Toss in while there because it’s cheap and they will be right there. I’ve also had the code for awhile.


Sent from my iPhone using Tapatalk