2008 R55 with approx. 126k miles. Months ago I began noticing a lot of white smoke coming out of the exhaust after a warm start (for example, stopping to get fuel on the way home from work). It also smoked a tiny bit from under the hood, but 95% was out the exhaust when taking off from a light and it would eventually go away after a few minutes of driving. Not long after this the water pump gasket began to fail. The cheap aftermarket valve cover was also beginning to leak a bit of oil. So recently I replaced the following: water pump, friction wheel, belt tensioner, valve seals, and valve cover. I also cleaned the throttle body and mass air flow sensor while I was at it. I also have a mile long list of other parts that have been replaced within the last 3 years on this car…
While doing my test drive to the gas station to fill up the car drove better than ever. I filled up the tank with 93 octane and before I even made it out of the parking lot I noticed the car stumbling a bit white taking off in 1st gear. A few seconds later I noticed white smoke pouring out the exhaust, STILL! I was really hoping the valve seals were the cause of this but apparently not.

I parked and popped the hood… White smoke was sputtering out of the exhaust and the engine was surging at idle. It acted like it was struggling to stay running for a few seconds because of the RPMs dropping below normal, then it would regain composure and idling smooth. This happened multiple times while I was parked trying to investigate. One thing I did notice while standing at the back of the car was that the white smoke smelled a lot like fuel.

On the way home I went through the gears getting up to speed quickly and while under acceleration the car seemed to do fine, yet white smoke was trailing behind me for miles. So much that I had a hard time seeing out my back windows. I’m now at a loss on what to check next. I’ve been reading forum posts from other MINI owners who have had the same “white smoke out the exhaust” issues and haven’t come across anything that seems similar to my particular issue. Most report burning excessive oil or a coolant leak, which I don’t seem to have.

There is a local indie mechanic that works on turbo cars a lot and he said to drive it until it throws a code, because so far it has not given any codes or CELs. He did say that if the smoke smelled like fuel it could be a faulty fuel injector or maybe something to do with the high pressure fuel pump. I don’t want to replace the injectors without first knowing one or more is absolutely bad. Not sure how to diagnose that… Any suggestions on what to check next would be appreciated. Thanks!

 

Are you sure that you didn't blow the head gasket

 

White smoke usually means coolant, blueish smoke for oil, and dark or black smoke for fuel…

 

I guess my next step would be to pressure test the coolant system then. I’ll have to get a better picture of the smoke while someone is revving the engine to post and see what everyone here thinks. Some might call the smoke blue but I went with white when describing it. If coolant was the cause wouldn’t my expansion tank level be decreasing? I haven’t lost any coolant. I would think this much smoke it would have to be leaking pretty significantly.

 

The other part of my gut wants to say that if the smoke dissipates quickly, its likely water vapor from the coolant. If it lingers, then it might be oil....

 

Before I changed the valve seals it would go away after a few minutes of cruising. But this last time it just left a trail of smoke behind me the entire way home. And when I pulled in the driveway both exhaust pipes were like a smoke machine on full blast. It didn’t seem to be dissipating at all this time… If I have time after work today to drive it again and replicate the symptoms I’ll get some pics and video for reference.

 

I guess its possible the turbo is starting to leak oil past the seals? Based on everything you already replaced, I can't think of anywhere else that much oil could be getting into the exhaust...

 

Possibly… when the car had around 100k miles on it I had no boost, which ended up being the vacuum lines but I also replaced with another OEM turbo with less miles, as well as exhaust manifold gasket, foil ring gasket, as well as all hoses and lines running to/from the turbo. I used stainless braided lines where I could. I think I’ll have to put more miles on it to see what the oil consumption is like.

 

So I just went for another 2-3 mile drive to warm the car up. After first startup I scanned it with the torque app and it showed code P2185 O2 Sensor Signal Stuck Lean bank1 sensor1. I cleared that code, went for a drive (car is driving fine…), stopped at a light and that’s when I notice it idling a little rough and a very small amount of white smoke out the exhaust. Upon acceleration the car felt and sounded fine and I didn’t notice any smoke.

I pulled into my driveway and let it idle for about 10 seconds, just long enough to notice idle has become more sporadic. I let the car sit for 1-2 minutes before having my wife start it so I could look at the exhaust and take pictures and video. Side note: I tried uploading a short video and got a message that just said “Alert” so I guess it’s too large or I’m not doing something right? Any input on how to upload this would be helpful. I’m not savvy with electronics these days…

But it began smoking quite a bit upon this warm start, when my wife revved the engine the smoke dissipated some and started back up during the surging idle. I stopped the car and scanned again and got a different code, P2097 Post Catalyst Fuel Trim System Too Rich bank1.

Also, I’m keeping a very close eye on coolant and oil levels in between drives. So far they haven’t deviated. It’s worth noting that these codes were showing as pending and the car never gave me a CEL.

 

With those two codes, maybe the 1st O2 sensor is going bad....

 

Exactly what I was thinking, and hoping. I just ordered a Bosch O2 sensor for $110 and change. I’ll know in 3-4 days if that makes any difference. Fingers crossed! 😬

 

Got the new O2 sensor delivered yesterday. I started the car before installing to see if it was throwing any of the same or different codes. This time it has P1631 and the half lit CEL. If I tried clearing this code it immediately popped back up.

Once replacing the oxygen sensor and started the car there was no CEL and this code cleared fine without returning, BUT the car is still smoking pretty badly once warm. I’m going to drive it more and continue to monitor the oil level. I think it has to be leaking oil somewhere within the turbo to be causing this much smoke.

 

Thought I should update this thread... So originally I do think the smoke I was seeing was from the valve stem seals, but then when it became more significant and CONSTANT was awhile after I had the car smoke tested to determine there was a couple holes in my vacuum lines. Lines were replaced and the turbo got it’s life back… for a bit. At that point the turbo was on its way out and I believe the main shaft seal failed because I had oil all throughout the intercooler. I put a different OEM turbo on, as well as an upgraded intercooler and the car was running great for about 3 days. I got on it hard in Sport mode and it sputtered and gave me a half lit CEL. Codes said I had a misfire on #2 and #3 cylinder. I could only get the misfire to replicate on cylinder #2 after that though. But just in case, I replaced all 4 ignition coils after determining one coil was for sure bad (I moved it to cylinder 3 and 4 and the codes followed). The car runs great again, FINALLY. Lastly, I was getting a P1631 power train code at cold starts that threw a CEL. The throttle body was faulty and wouldn’t pass the test at startup if the cat was cold. I replaced the throttle body and that fixed the issue. For the first time since I’ve owned this car I have zero engine problems and now just need to fix/replace some exterior trim since BMW plastic abs rubber is total GARBAGE!

 

Thanks for the update - glad to hear you figured it out!