Lots of smoke coming out of o2 sensor (vid included)

blakekald · 12-12-2020, 10:00 PM

Hi guys!

Above is a video of the problem I'm having.

N55, upgraded fmic, intake, exhaust, catless downpipe, MHD stage 2+.

For the past 3-4 weeks the car has smelled like there was plastic burning somewhere. About 2 weeks ago after driving the car moderately hard, a decent puff of smoke came out of the hood when I went to park.

I looked around and noticed there was a small leak from my VCG, so I replaced that about 6 days ago hoping that would fix the problem.

I pressure washed the downpipe and the o2 sensor to get all the old oil off as best as I could.

After another moderately hard drive today, the car started smoking again and I recorded the video above.

Any suggestions as to what it could be? It smells like burning plastic.

Cal96 · 12-12-2020, 10:48 PM

did you look under the 02 area? maybe some plastic got hot and melted down to the exhaust

thejeremyman9 · 12-13-2020, 12:00 PM

Looks to me like something is still leaking on the DP and burning off.

MTWO · 12-13-2020, 10:25 PM

Oil leak, maybe from the valve cover?

blakekald · 12-13-2020, 10:51 PM

Quote:

Originally Posted by MTWO

Oil leak, maybe from the valve cover?

Hi, I replaced the valve cover gasket a week ago and when I had it off fully checked the valve cover and everything looks great.

Quote:

Originally Posted by Cal96

did you look under the 02 area? maybe some plastic got hot and melted down to the exhaust

I don't have a way to lift the car at the moment. Tuesday I'll bring it to my buddies lift and completely take a look at it.

Quote:

Originally Posted by thejeremyman9

Looks to me like something is still leaking on the DP and burning off.

Yeah, that's old oil. I haven't been able to get that off at all. That exact streak you see has been there for over a month. I'm mainly concerned about the plastic smell that I smell and the smoke coming out of the o2 sensor.

This Tuesday I'll take the downpipe off and completely clean all the old oil residue off.

5w20 · 12-14-2020, 01:29 AM

Old oil residue or that vc gasket is still leaking.

DrivingPassion · 11-15-2021, 06:59 PM

What did you find blakekald ?

I'm having the same thing happening on my F22 with N55 engine.
I have also just replaced the VCG because I thought it was the main reason for the smoke.

For my case, I have hand wiped the O2 sensor with rubbing alcohol and it is all nice and clean. I used my bare hand to feel around and smelled my fingers and there were no oil on it.
But, after the engine warms up, smoke start to escape from the O2 sensor again and it has a burnt smell.

I have a new O2 sensor ordered and it is on the way.

NEWTRON · 11-15-2021, 07:26 PM

Quote:

Originally Posted by DrivingPassion

What did you find blakekald ?

I'm having the same thing happening on my F22 with N55 engine.
I have also just replaced the VCG because I thought it was the main reason for the smoke.

For my case, I have hand wiped the O2 sensor with rubbing alcohol and it is all nice and clean. I used my bare hand to feel around and smelled my fingers and there were no oil on it.
But, after the engine warms up, smoke start to escape from the O2 sensor again and it has a burnt smell.

I have a new O2 sensor ordered and it is on the way.

I doubt the issue is with your o2 sensor. The Smoke starting after the car warms up tells me its oil possibly still leaking from the VC. The VC is plastic and sometimes warps or cracks from the heat, preventing the gasket from sealing properly.

thejeremyman9 · 11-15-2021, 09:02 PM

Quote:

Originally Posted by DrivingPassion

What did you find blakekald ?

I'm having the same thing happening on my F22 with N55 engine.
I have also just replaced the VCG because I thought it was the main reason for the smoke.

For my case, I have hand wiped the O2 sensor with rubbing alcohol and it is all nice and clean. I used my bare hand to feel around and smelled my fingers and there were no oil on it.
But, after the engine warms up, smoke start to escape from the O2 sensor again and it has a burnt smell.

I have a new O2 sensor ordered and it is on the way.

Did you clean the DP, turbo manifold, and everwhere else oil leaked? As mentioned above it probably just looks like its coming from the O2 sensor.

lazyb0ne · 02-01-2022, 04:05 PM

Quote:

Originally Posted by thejeremyman9

Quote:

Originally Posted by DrivingPassion

What did you find blakekald ?

I'm having the same thing happening on my F22 with N55 engine.
I have also just replaced the VCG because I thought it was the main reason for the smoke.

For my case, I have hand wiped the O2 sensor with rubbing alcohol and it is all nice and clean. I used my bare hand to feel around and smelled my fingers and there were no oil on it.
But, after the engine warms up, smoke start to escape from the O2 sensor again and it has a burnt smell.

I have a new O2 sensor ordered and it is on the way.

Did you clean the DP, turbo manifold, and everwhere else oil leaked? As mentioned above it probably just looks like its coming from the O2 sensor.

Hiii did you figure out how to fix that?

StansF30 · 03-18-2023, 10:24 AM

Quote:

Originally Posted by lazyb0ne

Hiii did you figure out how to fix that?

Did anyone in this thread find a resolution? Having this exact issue.

SuperLomi · 03-18-2023, 08:14 PM

This is 100% a leaking valve cover gasket. Oil runs along the heat shield and drips down onto the cat.

n55david · 03-20-2023, 07:19 AM

Quote:

Originally Posted by StansF30

Did anyone in this thread find a resolution? Having this exact issue.

Valve cover leaking

SparkyBarbs · 09-18-2023, 10:41 AM

Did you ever find a resolution? I am having the same exact issue of late.

SparkyBarbs · 09-18-2023, 10:51 AM

Quote:

Originally Posted by StansF30

Did anyone in this thread find a resolution? Having this exact issue.

Did anyone figure out the cause and solution?

thejeremyman9 · 09-18-2023, 03:06 PM

Its most likely VC leaking, as noted in the responses above

lucasborka · 09-19-2023, 05:49 AM

Did you clean the heat shield when replacing valve cover? Oil could still be there and drip on the downpipe

12-12-2020, 10:00 PM	#1
blakekald New Member 5 Rep 16 Posts Drives: BMW 335i Join Date: Sep 2020 Location: SoCal iTrader: (0)	Lots of smoke coming out of o2 sensor (vid included) Hi guys! Above is a video of the problem I'm having. N55, upgraded fmic, intake, exhaust, catless downpipe, MHD stage 2+. For the past 3-4 weeks the car has smelled like there was plastic burning somewhere. About 2 weeks ago after driving the car moderately hard, a decent puff of smoke came out of the hood when I went to park. I looked around and noticed there was a small leak from my VCG, so I replaced that about 6 days ago hoping that would fix the problem. I pressure washed the downpipe and the o2 sensor to get all the old oil off as best as I could. After another moderately hard drive today, the car started smoking again and I recorded the video above. Any suggestions as to what it could be? It smells like burning plastic.
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12-12-2020, 10:48 PM	#2
Cal96 New Member 3 Rep 12 Posts Drives: f30 Join Date: Aug 2020 Location: los angeles iTrader: (0)	did you look under the 02 area? maybe some plastic got hot and melted down to the exhaust
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12-13-2020, 12:00 PM	#3
thejeremyman9 Major General 4362 Rep 7,602 Posts Drives: 2015 BMW 335i Join Date: May 2019 Location: Cali iTrader: (0)	Looks to me like something is still leaking on the DP and burning off. Attached Images
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12-13-2020, 10:25 PM	#4
MTWO Captain 473 Rep 931 Posts Drives: M2 Join Date: Dec 2016 Location: Innisfil iTrader: (0)	Oil leak, maybe from the valve cover?
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12-14-2020, 01:29 AM	#6
5w20 @_sunbish 282 Rep 611 Posts Drives: Bmw 435i & 340i Join Date: Mar 2019 Location: Houston iTrader: (0)	Old oil residue or that vc gasket is still leaking.
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11-15-2021, 06:59 PM	#7
DrivingPassion Lieutenant 130 Rep 485 Posts Drives: '15 M235xi Join Date: Nov 2006 Location: WA iTrader: (0)	What did you find blakekald ? I'm having the same thing happening on my F22 with N55 engine. I have also just replaced the VCG because I thought it was the main reason for the smoke. For my case, I have hand wiped the O2 sensor with rubbing alcohol and it is all nice and clean. I used my bare hand to feel around and smelled my fingers and there were no oil on it. But, after the engine warms up, smoke start to escape from the O2 sensor again and it has a burnt smell. I have a new O2 sensor ordered and it is on the way. __________________ 2015 M235i xDrive 8AT
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03-18-2023, 08:14 PM	#12
SuperLomi First Lieutenant 204 Rep 383 Posts Drives: 2013 335i M-Sport Join Date: Nov 2020 Location: KY iTrader: (0)	This is 100% a leaking valve cover gasket. Oil runs along the heat shield and drips down onto the cat.
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09-18-2023, 10:41 AM	#14
SparkyBarbs Registered 0 Rep 2 Posts Drives: 2015 435xi Join Date: Sep 2023 Location: CT iTrader: (0)	Did you ever find a resolution? I am having the same exact issue of late.
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09-18-2023, 03:06 PM	#16
thejeremyman9 Major General 4362 Rep 7,602 Posts Drives: 2015 BMW 335i Join Date: May 2019 Location: Cali iTrader: (0)	Its most likely VC leaking, as noted in the responses above
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09-19-2023, 05:49 AM	#17
lucasborka Private First Class 40 Rep 185 Posts Drives: BMW F36 435i FBO Join Date: Nov 2019 Location: Sweden iTrader: (0) Garage List 2015 BMW 435i [7.50]	Did you clean the heat shield when replacing valve cover? Oil could still be there and drip on the downpipe
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