Rebuild engine after 600 miles - Oil smells again like fuel

JohnDaviz

Sergeant
Jan 6, 2019
349
192
0
Ride
335i E92 DCT
Hi all,

recently i had the pleasure to rebuild my engine due to a spun rod bearing on cyl 3.

It was literally so worn out that one bearing half was as thin and bendable like aluminum foil. The Rod has some fancy coloring now too.
After the failure we opened the oil cap and the oil smell was as there was fuel in it.

With the new engine it is the same. Just after 30 miles the oil smelled like fuel. After 600 Miles now it literally still smells like fuel again. Even after driving for 100 miles and hot oil. Coming to a stop - it does not smell like oil.

I compared to a C43 2019 model (only comparison i could do in short term) with 2400 miles on it and the oil smells like oil.

I now started to watch AFR through MHD and there is something strange going on.

Bank 1 AFR drops to low 13ish values when coming to a stop at a traffic light and it needs a fews seconds to come back to the same level as bank 2. Always with every stop.

Also when getting off the throttle bank 2 afr seems to go immediately to 234 but bank 1 not. Feels like its taking forever.


I had to accelerate again but you can see the value dropping shortly to 13 something.

I have my doubts that this is normal?!

My next steps are to control the spark plugs and if one or more seems to be running rich.

Oil changed after 600 miles and new filter. So far no metallic parts. I am really paranoid because of the smell.


I also have a log of what i mean:

https://datazap.me/u/johndaviz/afr-rich?log=0&data=3-15-16-22
 

1and1

Specialist
Dec 28, 2016
60
34
0
Tally, FL
How much of a rebuild was done? New rings and hone the cylinders?
Just a couple of basic thoughts- are the injectors in good shape, and have you performed compression test/leak down test?

Thinking is an injector is misbehaving, not only causing the wonky afr's, but is pooling enough to run down the cylinder wall and into the bottom end/oil.
 
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JohnDaviz

Sergeant
Jan 6, 2019
349
192
0
Ride
335i E92 DCT
Engine was rebuilt completely. So yes. Honing and new rings.

I cant explain that AFR behavior. It is really strange.
 

Mzfhartge

Specialist
Aug 17, 2017
52
17
0
Somerville, Ma
Ride
07 bmw 335i
start the car for little bit and then immediately after you shut it off take spark plugs cylinder 3 and see if its wet. Check cylinder 1 and 2 also while you have there and report back. If its wet then guaranteed injector on cylinder 3 is leaking, replace it and code it.
 

doublespaces

General of the Army
Oct 18, 2016
8,940
4,145
0
AZ
Ride
2009 E93 335i
Sounds like leaking injector that is chewing through your oil on these surfaces.
 

Icewall

Lurker
Nov 3, 2016
18
13
0
NJ
Afaik theres mainly 2 ways you can be running rich like that.

Bad injectors or fuel is being pulled through the vent line of the throttle body but that would make both banks rich (happened to me)

Whats the shape of those injectors??? Swap them to bank 2 and see if bank 2 goes rich. That should tell you if they are bad.

And as was already suggested, check spark plugs and compare them to bank 2s plugs.
 

Mikejones1208

Corporal
Dec 6, 2016
115
96
0
Savannah, GA
Ride
2009 BMW 335i
One of the guys on here pulled them and left them connected to find the leaker
Thats how ive checked them in the past, pull them, flip the fuel line around re connect the fuel line but leave them unplugged then prime the system a bunch of times untill fuel pressure is as high as you can get it without starting the car and look very closely with a flashlight, one injector had such a small leak the fuel was actually atomizing and flying off the wind lol, didnt even leave a drop on the towel , but leaking none the less