[bmwak]

Hi all,

So my N53 325i was light smoking for a while (believed to be oil dripping onto manifold and smoking as there was a oil burning smell too). It ended up making the Lambda probe on bank 2 (pre-cat) giving up ghost, as the oil was dripping on this.

So I decided to fit a new lambda probe, cleaning the area as much as possible with brake cleaner etc. The old lambda was hard to get off, so I had to use quite a bit WD-40 on the manifold and even spray some overnight for it to easily come off the next day.

I also decided to renew the valve cover gasket, as it would only happen again if I let that continue. Everything was changed out perfectly and torqued down correctly (9nm) as per BMW specs.

Once complete, I started her up to find that idling was a bit erratic, misfiring and getting to the point where it was cutting out or almost cutting out. I took the car out for a short drive and came back and it was better but not perfect. The engine noise was louder than normal towards the back and when I took it for a drive and came to a stop, it smoked really badly (to the point where smoke came into the cabin). If I continued to move it would go away but would come back when I came to a stop.

I did change the spark plugs also and noticed a tiny bit of oil in some of the spark plug wells. Whilst I was prepping the valve cover for the gasket my friend who was helping gave the spark plug wells a clean with some carb cleaner (I wouldn't have used this but I guess its no real issue).

I know these plastic valve covers like to crack but I thoroughly inspected it and it seems fine. The gasket is sealed fine (i.e. not pinched). The breather hose is also fine, connected properly and not damaged, from what I can see.

Changing the valve cover gasket involves taking the fuel lines, rails and coilpacks and wiring off, so quite a involved job but I am 100% sure everything went back on perfectly as I double checked it all before starting up.

I am now stumped as to what it could be? I'm assuming the smoke might be to do with the WD-40 residue on the manifold as it is odourless smoke not like oily smelling smoke.

A fault code read brings up '2A2C Mixture Control 2' but nothing to do with misfires on cylinders or anything else.

Anyone have any pointers please or experienced similar?

[micdev42]

Hi, I replaced my VC gasket on my 325i a few months ago and documented what I did here:
https://www.bimmerforums.co.uk/threa.../#post-3336868

Note the bit about using 3-in-1 (or similar) oil in the gasket housing on the VC and on the head itself. This made sense to me and although a bit messy, I felt I got a good seal. Just a suggestion - which I know is a bit late now that you have done the job...
Other than that it seems you have covered all the bases. I didn't do anything with lambda sensors. Good luck.

[bmwak]

Thanks for the reply Micdev. I had a read at your 'how to' and pretty much did the same as you. I didn't use 3 in 1 oil but gave the gasket a thin coat of engine oil. I also used an Elring gasket to do the job.

As well as a new Bosch lambda sensor on bank 2, I also fitted new NGK spark plugs. Having scanned the car yesterday, it appears I now have combustion misfire codes for cylinders 4, 5 and 6.

So it all seems to be related to bank 2. I think the clouds of smoke is just residue WD-40 and oil burning off (I hope) from the bank 2 manifold.

[micdev42]

With it all being bank 2 it does sound like that lambda sensor is the issue. Is it easy to remove, clean and refit?

[bmwak]

So had success in resolving the issue.

I decided to re-trace my steps, focussing particularly on bank 2. After investigating I found that the earth stem in bank 2 had twisted the gasket around this and the surrounding area, which caused a pinched fit on the inlet side. This resulted in a vacuum leak, causing all these fault codes and lumpy idle.

I decided to take it all apart and fit another Elring valve cover gasket, buttoned it up enough to start it and it seems to idle happily. I took it for a quick drive and it still smokes (I'm guessing this will take time to clear/residue) but otherwise it runs perfectly. A fault code scan comes up with nothing so seems to be all good.

So moral of the story is when installing the earth stems, it is probably best to be the last thing to install, after all bolts are on and torqued up to correct torque.

[motornuts91]

i have the smoke problem when starting in the morning ..so i gues i need to replace the valve cover gasket?

[Phil325i]

Originally Posted by motornuts91

i have the smoke problem when starting in the morning ..so i gues i need to replace the valve cover gasket?

Not necessarily. Is it smoke or steam? These engines create a lot of condensation when the whether's cold. Smoke could also be failed injector(s) or even head gasket (though much less likely). Suggest you have the car read for fault codes...