[Shanusascarabus]

Hi, this is my first main post on this site regarding any issues on my car... or possible issues...
To start with my car is a 2006 E92 335i ( Auto )... box standard ( no upgrades ) and i have had it just over a year now with no major issues but i'll list what I have done and issues i'm starting with..
So not too long after getting the car I got P0420 errors... changed both pre CAT sensors ( bank 1 and 2 )... problem went away..
Ive always had an issue with oil loss ( I replaced OFHG twice ) and it no longer leaks but i'm still using or burning oil quite a lot.... I get a burning oil smell but no visible signs of a leak... but at the same time no smoke from the back.
Anyway after a trip at the weekend a couple of odd thinks happened which has made me look into this a little more..... firstly going down a hill the revs seemed to stick at approx 3500rpm and drop to the normal 2k after tapping accelerator.... after messing i could bring this on myself by foot to the floor and letting off of accelerator... revs drop to 35500 and stay for a while or till i tap accelerator again.... so could this be gearbox maybe ??
also the car asked for its monthly 1L oil top up so did this also..... anyway dont ask me why but i `plugged torque into the car and it came up with P0420 and P0430 ( Both O2 sensors ) at the same time so im starting to think that oil is actually getting burnt off somehow without the smoke... possibly clogging up the Cats ???
Another thing is i'm wanting to Walnut blast the intakes as i don't think they have ever been done ( i'm at 90k )..... at the same time i'm thinking PCV valve.... but maybe instead of just putting the RB PCV on I should just change the whole Valve cover and gasket as i'm guessing the internal PCV system built into the cover could be blocked up or restricted.... as well as eliminating whether the Valve cover itself is leaking oil somewhere out of view.

So a short version would be... is it worthwhile getting a walnut blast while the car has these issues..??
Can I test the PCV somehow to know for sure if i have an issue there ??
is there a safe method of "flushing" the engine to clear any built up gunk inside and hopefully clean the system out ??

I really don't want to just throw big money chasing problems... as potentially a walnut blast, Valve cover,Cats,Sensors, turbos/seals checking over along with pipework would run into thousands

Just to add the car runs great and still pulls like a train

Cheers Guys

[Shanusascarabus]

Wow.. nothing

Well I guess I should at least get the walnut blast done.. then at least I know for sure that the intake side is clean and she is breathing better, I just wasn't sure that if I had issues elsewhere then the intakes would clog up in no time

[therealdb1]

Ok I'll answer.
For what its worth, if the car is driving well why spend money polishing the inlets when there is probably nothing wrong in that area and you have a problem with oil consumption?
You do not say how many miles you drive in a month so a litre of oil may or may not be excessive.
However, to me you are answering your own question. You had lambda sensor faults, replaced the sensors and cured the faults. Now with burning oil smells you have lambda sensor faults back again.
I would hook up a diagnostic tool like INPA that lets you look at the lambda sensor outputs in real time to see if they are working. If they appear sluggish to respond or do not respond at all I would remove them for inspection and you may find that they are black in which case you will know where your oil is going. After that you need to find out how the oil is getting into the combustion chamber. Disconnect any hoses that lead to the inlet and see if there is oil when they should only carry air. It is probably not piston rings otherwise you would notice poor performance but there is no harm in a compression check. Valve guide seals are a possibility but I would strip down and check out the PCV system as the crankcase may not be breathing correctly and creating pressure where there should not be any.
Once you solve the oil consumption issues and replace the lambda sensors and possibly cats you can pickle your walnuts if you like!

[Shanusascarabus]

yeah your right I guess, it came out as a huge outburst.... typing what i was thinking... and pretty vague
I am guessing that its needing a 1L top up at around every 1000 miles going by my average.... I will be keeping an eye out for a more accurate count now its still leaking from somewhere, even after the OFHG replacement.

Also I don't have any software other than the torque app so a pm as to where I can download it would be very welcome ( would save me ages and a fair few virus's ).

The walnut blast had been my next thing because of the state of the inlets ( quite bad after inspection )... and had read that it can lower oil consumption perfect for my slight issue )... restore lost power and if your lucky give you a couple of mpg increase... basically a bit of preventative maintenance.

Im far from being a mechanic so my car expertise basically comes from google, so with that in mind... if my inlet valves are so clogged up and not sealing properly then could oil/vapours be entering the combustion chamber that way ?

Here is a picture I took of my inlets a few month ago....

[therealdb1]

It's difficult to tell from the photos but were the inlets wet?
They look pretty grotty but there is no point cleaning them until you are certain that you are not sucking oil in there.
If your valves were not sealing properly enough to allow oil in I would expect you to notice the running being rough. There should not be any oil around the valve seats anyway.
As for INPA I got mine from ebay when I bought the lead but most BMW forums have links to where you can download the software. The only downside to INPA is you need a laptop and patience to install it but once you have it you wonder why everyone doesn't!

[Shanusascarabus]

Thanks again,

Ill try and trace a copy when i get the time... i'm guessing installing it is a ball-ache.

The oil issue is a real pain too... wherever you read there are literally millions of possible causes, all of which are pretty common and not obvious without professional and expensive diagnosis... knowing my luck its a little bit of each one

[Wolf 335]

No leaks on top of the downpipe?

[Shanusascarabus]

Originally Posted by Wolf 335

No leaks on top of the downpipe?

Not that I can see, but i cant say 100%.... i really need to take the engine cover off and have another poke around.
I have looked around this area as a possibility of the valve cover leaking before but there was nothing obvious and on seeing oil around the other side of the engine I settled on the OFHG

[bishbosh]

Also you might want to check that the EGR valve is good and not gunked up. As the first person to reply said, check the pcv system, if you have the old loo roll filter this can be replaced with the improved vortex filter. The loo roll one tends to block up.

[Shanusascarabus]

What's the loo roll filter ??

[bishbosh]

I possibly had a brain freeze and that might only apply to diesels :/

[Shanusascarabus]

Haha.. thought so when I heard egr....

Well removed engine cover today and it's looking like a valve cover gasket issue to me.... see what you think ??

Not sure how the pictures will look but a puddle of oil in the hole... and on the thread of spark plug 3

[Shanusascarabus]

Just a mini update, definitely a leak somewhere as I have oil on the lower engine cover...
I noticed it while replacing the headlight washers ( front bumper off job ) so back to the drawing board...

I know the prefered thing to do would be to replace the valve cover as it comes with pcv valve, bolts and gasket but it also comes with a price tag over £300 so I might just risk a £20 gasket for now.... is there a preferred brand and is there any way of just checking if the pcv valve is working ??

[Wolf 335]

Originally Posted by Shanusascarabus

Just a mini update, definitely a leak somewhere as I have oil on the lower engine cover...
I noticed it while replacing the headlight washers ( front bumper off job ) so back to the drawing board...

I know the prefered thing to do would be to replace the valve cover as it comes with pcv valve, bolts and gasket but it also comes with a price tag over £300 so I might just risk a £20 gasket for now.... is there a preferred brand and is there any way of just checking if the pcv valve is working ??

Do a thorough inspection of the cover for cracks before you do anymore work.

[Shanusascarabus]

I have looked already but I can't see any obvious damage... and I have a feeling I won't see anything till al least when I remove the cover and look closer.
Are the filler caps known to leak ?

[AWSAWS]

Hi OP,

firstly about the oil consumption. You are probably on fairly old turbos so I'd wonder if the seals are just at the point where they leak a little but continuous amount of oil. Not enough for blue smoke but enough to mean regular top ups and a burning oil smell. As you'll know oil in the exhaust will do that. This combined with the fact that the PCV system does send alot of oil back through the inlets, helping in the gunking of your inlet valves. It's perfectly normal to find a good deal of oil in the charge pipes of these cars. Even the valve overlap used to reduce NOx is supposed to make the valve carbonisation worse.

TBH at stock power and without issues like misfires or idling problems I wouldn't think a walnut blast is necessary. However it's up to you and it depends on how long you plan to keep the car. I've had it done myself on a car with up-rated turbos to get the maximum amount of airflow through the standard head. The cost is something like £300 to £350 with a good independent garage.

The oil on the engine near cylinder 3 is most likely oil that was spilt when doing an oil change. Without using a funnel it's very easy for oil to spill and end up down there.

I replaced my PCV with the RB valve. It sometimes dribbles oil down the back of the engine near cylinder 5 and 6. At first I though I had the valve cover gasket leak. I wiped it down and it hasn't returned after a few months and plenty of wide open throttle runs. If the engine is mucky then wipe it down and see if oil returns. Get some paper towels to mop up that spill near cylinder 3 and see if that comes back also.

Good luck

[Shanusascarabus]

Thanks for the advice AWSAWS, yeah it's not a clear cut case on my car as nothing is obvious to the naked eye... I had noticed a long time ago that the spongy undercarriage of the engine cover was in fact saturated with oil and my first conclusion was the exact same... possible spillage from a previous oil change... that was over a year ago though so I'd have thought it would have cleared up.
I also get what your saying with a walnut blast.. as previously mentioned by others why do it if it's not needed... the thing is I have no issues at all just maybe a very slight idling mumble and a possible delay on acceleration... that's it.
I am Hoping to MHD the car as soon as im 100% happy that all is good just to see what all the hype is about and to see uf it makes a noticeable difference to performance

[Shanusascarabus]

Well today on the way home from work the car decided to spew the contents on the oil all over... a catastrophic leak from somewhere... possibly the rear lower part of the engine

[Shanusascarabus]

So as I've been using oil a while and I have been checking the level every day or two... 2 days ago it was full.... today it flashed up I was below minimum so I knew something was wrong... got home and started to look around the car... undertray was dripping oil everywhere....
Took the covers off the top and it was relatively dry... no sign of a catastrophic oil failure up there... as far as I could see the area around the turbos was quite dry... the oil seems to be coming from the rear of the engine.... dripping from the area where gearbox and engime meet... however access is a real issue for me and i cant see much... any ideas ??

[frenchi]

Rear main seal and oil pan gasket...pretty common on 335i. Gaskets are cheap but it takes about 8-9 hours of work to replace them

[Shanusascarabus]

Yeah that's my initial thought also..... i got it booked in on moday for a diagnosis and price....gulp !!

[Shanusascarabus]

Just so I know i'm not getting fleeced, is there a pretty average price id be looking at on either job, its at a BMW independent specialist not a main dealer so that should hopefully shave a fair few quid off