[E92Stock335i]

Hey Everyone,

New here and my first post so please go easy. A month ago a coworker noticed that there was some blue smoke from the exhaust at startup and yesterday I noticed that after downshifting from fourth to third and really stepping on it I saw some smoke from the rearview. After inspecting the exhaust in the morning at startup, I notice a brief puff of smoke which looks more grayish/blackish to me then blue at all. After I start the car there's a brief moment before the smoke comes out a short rattle from the exhaust and then the smoke from the right exhaust. Today after i got home from work I had a friend rev the engine before I shut the car off and only about after the tenth time did I see a small puff of grayish/blackish smoke from the left exhaust. Any ideas that point to one thing based on the evidence? Some facts on the car-2007 335i 6MT coupe completely stock. Just ticked over 146k miles thanks to my 90 mile round trip commute for the past three years. Got the car in 07 with 10k miles on it. I've had the spark plugs changed about 15k miles ago as well as the water pump and thermostat. Oil filter housing gasket and "intercooler tube o-ring" about 25k miles ago. Oil changes every 5k miles since ticking over 100k and sometimes I need to add a quart just before I reach the next oil change and sometimes I don't. Was averaging 26.1mpg before recently dropping to 25.8 this summer. My commute is mostly highway miles with a mix of cruise control at 75 mph and some spirited passing and on-ramp fun. Car has had turbos replaced due to wastegate rattle, HPFP replaced twice and fuel injectors replaced while it was under CPO warranty. Might I also add the car runs great! Still pulls strong and has been reliable since all those major repairs from the dealer. From my searches here I plan to have the following preventative maintenance that have never been done at my next oil change and again just looking for some feedback: valve cover gasket, serpentine belt, walnut shell blasting intake valves, RB pcv-valve and cap. Anything else you guys would recommend they do while they have it relative to the smoke issue or even just in general? I must apologize for the novel I just wrote but wanted to provide all the relevant information that I could think of. Thanks in advance!

[atinybug]

Blue smoke is burning oil, it's most likely a leaky VCG, especially at close to 150k miles if you're still on the original one.

[E92Stock335i]

Update: I just had the VCG replaced, walnut shell blast, and RB PCV valve upgrade done and still getting the brief puff of smoke at startup. Car is otherwise stock and never modded. Anyone have any other ideas?

[kiel_dafo_kenyg_as]

Greyish/blackish is the natural color of burnt fuel. Have you modified the sparking plug openings (which is a nono)? Either you have weak sparks or the engine may have dirty combustion caused by worn injectors. Is the engine a bit rough at idling?

[E92Stock335i]

Have had some intermittent rough idling at startup but hasn't happened since previously mentioned service has been done. I've only had it back two days so not sure if it will reoccur. No modifications to the spark plug openings and the plugs were replaced about 20k mikes ago.

[Kwike92M3]

Originally Posted by atinybug

Blue smoke is burning oil, it's most likely a leaky VCG, especially at close to 150k miles if you're still on the original one.

A valve cover gasket leaking would produce smoke from the engine bay/odor in the cabin. VC gasket cannot cause smoke from the tailpipe.
Most common issue is bad PCV. However, if that has just been replaced, there is a good chance that the piston rings are bypassing oil and burning it off in the combustion chamber. We have seen many high mileage BMWs have this problem. There is not much you can do for oil consumption issues of this nature, minus an engine tear down and rebuild.

There is always a possibility there is a different problem, but this has been my experience in the past. Good luck.

PS: I am not a proponent of any type of "mechanic in a can" but i have heard some decent results (true or not) from using a lucas additive. Use at your own risk.
Keep in mind that oil is what drives VANOS and timing chain tension, lubricates turbos (pending application), etc.
I would not use lucas in my own vehicles.

[Kwike92M3]

Also, seeing that this is a turbo, there might be a chance that the turbo is causing oil consumption. Maybe this is an excuse for an upgraded turbo

[Miller335]

My guess is turbos or valve stem seals.

[E92Stock335i]

At most the car is burning about 1qt per 5k miles. Is that reason to be alarmed or just par for the course for this engine? From what I've read on the forums its either a leaky fuel injector, bad turbo seal or leaky piston rings. Is there a way to easily rule any of these out? Would posting a video help?

[Kwike92M3]

A leaking injector is not the fault here. If there were a leaking injector, you would typically be seeing rich condition codes (mixture codes). If you are truly interested in having the problem fixed, then take it to a reputable independent shop. But be prepared for a laundry list of repairs and expensive initial diagnostic if tear down is required.
Otherwise, add oil, drive the car like you stole it, and move on with life.