New O2 sensor (Bank 2, Sensor 1) flatlined

[aaronknotty]

Sorry I posted this originally in the E39 Wagon forum by accident instead of here. So if there an admin that wants to take it down over there, that would be great. Cause I couldn't figure out how to go about that. Thanks!

Sooo, I'm been having cold start up issues with my car. First it would misfire most days on cold startup, then when its warm, you turn it off then back on and it's fine. Been trying to fix the issue. Finally started looking around the O2 sensors cause I honestly don't know if they have ever been changed and its at about 200,000 miles. The car recently had the top end rebuilt and everything that comes with that.

"2001 BMW 525i Wagon, M54"


To get a better picture of what is going on I cleaned up around the upstream O2 sensors cause there was some oil. Wanted to make sure there wasn't a leak in the valve gasket, so i cleaned it up to see if it would leak later. Well... since doing that my car ran fine. Then one day the mpg gauge showed 8mpg! and i was feeling a loss of power. Thought it was weird, so I shut the car down, re-satarted later and it was fine. Well now its stuck in the bad little habit. Plus theres now a Catalytic converter bellow threshold code (P0430) that popped up. I doubts its the Cat, cause i would't have been able to just re-set the issue like i did earlier if it was.


Like I said I narrowed it down to the O2 sensor area so i popped 2 new OEM Bosch sensors. And... no change. So I pulled out my very limited OBD Fusion scanner and pulled up the O2 sensors on the graph while running the car. Everything looks good except the Bank 2, Sensor 1 start up and then flatlines at the bottom of the graph. A.K.A my engine can't mix.


So!! the question that I have.


1. I guessing theres the possibility theres a short in the sensor wiring. But the fact that it started up then flatlined makes me think it may not? Or could that just be clunky OBD Fusion?


2. Are there fuses for the O2 sensor heaters? Is it possible i shorted a heater out during cleaning? Just used some brake cleaner on the outside of the connectors and under valve cover lip area. But all wiring is sealed so I feel like that could be ruled out.


3. Could a massive vacuum leak on the front affect this? I feel a large leak would affect both though...


4. Is there anything else I'm missing and should check?

5. I believe there could also be either a leak on the bank 2 exhaust manifold or issue with bank 2 injector.

6. All the current code are follows:
P0313 (Misfire detected with low fuel)
P0300 (Random/Multiple Cylinder Misfire Detected)
P0430 (Catalytic System Efficiency Below Threshold)
P1353
P1342




I have CSV file from a short test i ran on the car. You can obviously see that there is something wrong with O2 sensor Bank 2, Sensor 1. it gives off so little its literally off the chart except in the middle. But even that is low. And massively throwing off the fuel trim. For some reason I can't add attachments. So here's the data. Thanks!










Time, Engine coolant temperature (F), Intake manifold absolute pressure (psi), Engine RPM (RPM), Intake air temperature (F), Mass air flow rate (g/s), Absolute throttle position (%), Commanded secondary air status, Location of oxygen sensors, O2 voltage (Bank 1 Sensor 1) (V), Short term fuel trim (Bank 1 Sensor 1) (%), O2 voltage (Bank 1 Sensor 2) (V), Short term fuel trim (Bank 1 Sensor 2) (%), O2 voltage (Bank 2 Sensor 1) (V), Short term fuel trim (Bank 2 Sensor 1) (%), O2 voltage (Bank 2 Sensor 2) (V), Short term fuel trim (Bank 2 Sensor 2) (%), Input voltage read by the scan tool (V)
11/23/2018 02:04:14.3302 PM,199.4,0,0,96.8,0,5.882353,4,51,0.235,0,0.33,99. 21875,0,0,0.48,99.21875,0
11/23/2018 02:04:19.3081 PM,199.4,0,0,96.8,0,5.882353,4,51,0.245,0,0.34,99. 21875,0,0,0.475,99.21875,11.1
11/23/2018 02:04:22.7110 PM,199.4,0,0,96.8,0,5.882353,4,51,0.255,0,0.345,99 .21875,0,0,0.47,99.21875,11.1
11/23/2018 02:04:26.1308 PM,199.4,0,0,96.8,0,5.882353,4,51,0.265,0,0.355,99 .21875,0,0,0.465,99.21875,11.1
11/23/2018 02:04:31.2096 PM,199.4,0,0,96.8,0,5.882353,4,51,0.275,0,0.36,99. 21875,0,0,0.465,99.21875,11.1
11/23/2018 02:04:36.7866 PM,199.4,0,0,96.8,0,5.882353,4,51,0.285,0,0.37,99. 21875,0,0,0.46,99.21875,11.1
11/23/2018 02:04:40.8441 PM,199.4,0,0,96.8,0,5.882353,4,51,0.295,0,0.375,99 .21875,0,0,0.455,99.21875,11.1
11/23/2018 02:04:44.6793 PM,199.4,0,0,96.8,0,5.882353,4,51,0.3,0,0.375,99.2 1875,0,0,0.455,99.21875,11.1
11/23/2018 02:04:54.5990 PM,194,0,0,96.8,0,5.882353,4,51,0.31,0,0.38,99.218 75,0,0,0.455,99.21875,11.1
11/23/2018 02:05:05.7569 PM,194,0,632,96.8,7,0,4,51,0.87,0,0.755,99.21875,0 ,0,0.605,99.21875,11.3
11/23/2018 02:05:16.2536 PM,194,0,1610,96.8,16.8,0,4,51,0.085,0,0.865,99.21 875,0,0,0.86,99.21875,11.3
11/23/2018 02:05:27.1401 PM,194,0,981,96.8,5.32,0,4,51,0.35,-3.125,0.82,99.21875,0.04,27.34375,0.945,99.21875,1 3
11/23/2018 02:05:34.3493 PM,194,0,1569,98.6,17.71,0,4,51,0.065,-6.25,0.27,99.21875,0.04,27.34375,0.955,99.21875,13
11/23/2018 02:05:52.1215 PM,194,0,827,98.6,17.71,0,4,51,0.345,-3.125,0.14,99.21875,0.035,27.34375,0.95,99.21875,1 3
11/23/2018 02:05:55.6153 PM,194,0,731,98.6,5.25,0,4,51,0.195,2.34375,0.19,9 9.21875,0.035,27.34375,0.95,99.21875,13
11/23/2018 02:06:04.5008 PM,194,0,727,98.6,5.04,0,4,51,0.78,0.78125,0.315,9 9.21875,0.03,27.34375,0.95,99.21875,12.5
11/23/2018 02:06:17.6742 PM,194,0,715,100.4,4.97,0,4,51,0.05,-4.6875,0.795,99.21875,0.025,27.34375,0.94,99.21875 ,12.5
11/23/2018 02:06:22.1041 PM,194,0,721,100.4,5.04,0,4,51,0.785,0.78125,0.74, 99.21875,0.02,27.34375,0.94,99.21875,12.9
11/23/2018 02:06:25.5044 PM,194,0,1019,100.4,11.69,1.568627,4,51,0.87,-7.8125,0.845,99.21875,0.02,24.21875,0.94,99.21875, 12.9
11/23/2018 02:06:32.1765 PM,194,0,1019,100.4,28.14,22.7451,4,51,0.26,-4.6875,0.75,99.21875,0.005,14.84375,0.93,99.21875, 12.9
11/23/2018 02:06:51.2719 PM,194,0,1697,84.2,37.24,1.960784,4,51,0.195,1.562 5,0.825,99.21875,0,0,0.76,99.21875,12.9
11/23/2018 02:06:54.6780 PM,194,0,1035,84.2,4.9,0,4,51,0.08,3.90625,0.73,99 .21875,0,0,0.81,99.21875,12.9
11/23/2018 02:07:05.1512 PM,194,0,955,84.2,4.69,0,4,51,0.88,-1.5625,0.395,99.21875,0,0,0.865,99.21875,12.9
11/23/2018 02:07:37.1077 PM,194,0,1470,84.2,26.18,18.82353,4,51,0.785,-1.5625,0.825,99.21875,0,0,0.885,99.21875,13
11/23/2018 02:07:43.9513 PM,194,0,1340,89.6,19.04,7.843137,4,51,0.08,-3.90625,0.13,99.21875,0,0,0.795,99.21875,13
11/23/2018 02:07:51.7631 PM,194,0,1247,89.6,4.76,0,4,51,0.615,0.78125,0.69, 99.21875,0,0,0.775,99.21875,13
11/23/2018 02:08:15.4909 PM,194,0,1313,89.6,4.62,0,4,51,0.08,2.34375,0.77,9 9.21875,0,0,0.81,99.21875,13
11/23/2018 02:08:22.6311 PM,194,0,1167,89.6,4.62,0,4,51,0.775,0,0.665,99.21 875,0,0,0.81,99.21875,13
11/23/2018 02:08:35.9179 PM,203,0,1002,93.2,4.41,0,4,51,0.825,3.90625,0.625 ,99.21875,0,0,0.785,99.21875,13
11/23/2018 02:08:48.3626 PM,204.8,0,724,93.2,4.97,0,4,51,0.13,1.5625,0.775, 99.21875,0,0,0.775,99.21875,12.7
11/23/2018 02:08:55.2227 PM,204.8,0,724,93.2,4.83,0,4,51,0.655,1.5625,0.78, 99.21875,0,0,0.77,99.21875,12.9
11/23/2018 02:09:06.0664 PM,204.8,0,721,93.2,4.83,0,4,51,0.13,0.78125,0.775 ,99.21875,0,0,0.77,99.21875,12.9
11/23/2018 02:09:17.9870 PM,204.8,0,720,93.2,4.76,0,4,51,0.225,2.34375,0.77 5,99.21875,0,0,0.765,99.21875,12.6
11/23/2018 02:09:21.6039 PM,204.8,0,723,96.8,4.83,0,4,51,0.62,1.5625,0.78,9 9.21875,0,0,0.765,99.21875,12.6
11/23/2018 02:09:24.9389 PM,204.8,0,714,96.8,4.83,0,4,51,0.1,0.78125,0.775, 99.21875,0,0,0.765,99.21875,13
11/23/2018 02:09:28.6064 PM,204.8,0,714,96.8,4.9,0,4,51,0.55,0.78125,0.785, 99.21875,0,0,0.765,99.21875,13
11/23/2018 02:09:35.7337 PM,204.8,0,714,96.8,4.83,0,4,51,0.095,1.5625,0.775 ,99.21875,0,0,0.765,99.21875,13
11/23/2018 02:09:44.1664 PM,204.8,0,720,96.8,4.83,0,4,51,0.1,1.5625,0.77,99 .21875,0,0,0.845,99.21875,13
11/23/2018 02:09:51.3395 PM,204.8,0,1607,96.8,17.08,7.058824,4,51,0.095,-1.5625,0.3,99.21875,0,0,0.845,99.21875,12.8

[bmwdirtracer]

Hi Aaron, and welcome to the forum.

O2 sensors do not work until they reach ~600 degrees F. Therefore all cold engine O2 data, for the first minute, is immaterial at best.

I cannot begin to read that clump of stuff at the end of your post, sorry.

Sure, primary O2 sensors need to be changed every 100k miles....but your problem is on cold starts, so that's not going to be the issue.

I'd have to recommend (1) a smoke test of the intake system, (2) a crankcase vacuum test , and (3), realistically, a new set of spark plugs and coils. (Call it a tune-up, you're overdue anyway.)

The smoke test and CCV test will require a couple of pro-level tools....OR....you can buy a smoke machine for $140, and make your own CCV manometer for ~$20.. You can save a TON of money by buying OEM coils and plugs somewhere like FCP Euro, and doing that work yourself.

You're going to have to explain why you think the Bank 2 injectors are bad.

[aaronknotty]

Thanks! Well, the coils were actually just changed when the top end was rebuilt. But... the previous owner had a shop rebuild it. Which was a euro car shop, but that all I know about them. Sorry about the data, it’s CSV data that can just be pasted into a spreadsheet and it makes sense haha

The cold start and Cat issue I think are possible isolated things. At of my cat now O2 searching has been on a warm engine. All my cold start searching I can really only do once a day in the morning. Making that one harder to find.

The thought on the injectors is my total long shot guess, and could be way off. But my reason behind it is that since the pre cat O2 sensor is essentially stuck in a low signal (.004v). A long shot thought I had is that there could be a fuel issue getting that fuel to the cylinders causing the O2 sensor to look bad, even though it’s just doing it’s just. Haven’t be able to look at the injector system yet though. So that could not even be possible for all I know.

I tested both Bank 1 O2 sensor connectors for short and there were none.

I tried about every leak test possible without doing a smoke test, which may mean it’s just time.

The whole reason I cleaned the connectors in the first place was because it looked as if there is a valve cover leak. Leaking oil on things. So if that’s so, I could also be causing a leak.

[MarcoZandrini]

You car has an M54B25 engine. The engine computer (DME) ignores the O2 sensor data until the coolant temperature reaches a specific number. The sensor is located in the cylinder head between cylinders 5 and 6. During this cold start period the DME uses a rich fuel/air mixture. This gets the catalytic converters up to temperature quickly. I’m just wondering if the DME is, in fact, using the rich fuel/air mixture. Does the engine run at ~1000rpm for between 30 and 90 seconds? Does the secondary air pump (SAP) run during the same timeframe?
I think vacuum leaks would impact the idle at all engine temperatures, and not just cold starts. However, having owned a BMW with the M54 engine for 17 years, I concur with Chris’s recommendation to have the intake smoke tested, and to have the crankcase ventilation system (CCV) replaced. In the E46 these’s a small fuse panel under the hood . This contains a fuse for the O2 sensor heaters. I bet your E39 May have a similar fuse panel. Check your fuse panel card.

[aaronknotty]

You car has an M54B25 engine. The engine computer (DME) ignores the O2 sensor data until the coolant temperature reaches a specific number. The sensor is located in the cylinder head between cylinders 5 and 6. During this cold start period the DME uses a rich fuel/air mixture. This gets the catalytic converters up to temperature quickly. I’m just wondering if the DME is, in fact, using the rich fuel/air mixture. Does the engine run at ~1000rpm for between 30 and 90 seconds? Does the secondary air pump (SAP) run during the same timeframe?
I think vacuum leaks would impact the idle at all engine temperatures, and not just cold starts. However, having owned a BMW with the M54 engine for 17 years, I concur with Chris’s recommendation to have the intake smoke tested, and to have the crankcase ventilation system (CCV) replaced. In the E46 these’s a small fuse panel under the hood . This contains a fuse for the O2 sensor heaters. I bet your E39 May have a similar fuse panel. Check your fuse panel card.

Yeah when the engine is cold it starts up great for about 30-60 seconds. Then misfires start. Leading me to believe that the secondary air is working proper. Though I have not checked that yet. That’s what was also leading me originally towards the O2 sensor. Though I’m not sure if that’s responsible for the misfires on cold startup. I will check the fuses next to the computer though. Tried to yesterday and the screws holding the watertight case closed, just stared spinning. The reciving collars in the plastic tub are spinning, so I gotta figure how to get those out and export those things so the screws don’t spin haha the little things...

I’ll see if I can rent or borrow a nice smoke machine to test that first then follow up on other things. I did recently replace the Disa valve o-ring cause it fell apart. But, it made no change.

Cleaned the idle air control valve. It made no change. Though, the out tube on the idle air control valve is a little funky. And that could possible be an issue. But again, I feel like that would affect both banks, not just bank 2.

Looking at all of the CCV parts, I can see on the last mechanics invoice that all tube were changed. And I think the valve itself but not sure on that. As te last owner was unsure. I did test for vacuum when I open the oil filler to see if it sucks a plastic bag in a bit and the vacuum seems fine. Also I popped the top CCV valve hose off from the valve cover and there is a little white funk. But not much, curious if yet more due to the fact it’s been raining here a ton and that’s how moisture got in. But could also be a sign, cause I’m not super familiar with BMW engines.

I feel like I should also check the fuel pressure and see if that’s ok. But, I’m a little skeptical considering Bank 1 works great and Bank 2 has issues. Considering the fuel pressure is shared, I don’t see how that could be an issue unless it’s localized to an injector or two.

Thanks for your guys help! Really appreciate it!

[MarcoZandrini]

What’s happening is the engine runs find on the rich fuel/air mixture, and then runs like crap when the DME reverts to the normal mixture. First step is a smoke test as bmwdirtracer noted. The pre-cat O2 sensors can impact how the engine runs but not to the point where the engine misfires. Do the smoke test and see what happens.

[bmwdirtracer]

Hmmm, I'm wondering whether this car is running wide-band, pump-cell Zirconia sensors? Do your new sensors have 5 wires?

Pump cell sensors do not read voltages in the conventional manner, going from rich to lean to rich to lean, etc. They also do NOT put up with anything being squirted, or dripping into the air holes.

https://www.tiepie-automotive.com/en...nsor-broadband


If you have conventional sensors: Are you seeing Bank 1 sensor switching back and forth between ~0.2 volts and 0.8 volts, or so, very rapidly? Did you disconnect and swap both O2 sensors at the same time? (Could you have mixed them up?)


IF you have narrow-band sensors, and Bank 2 is indeed reading 0.004 volts, then the sensor is telling the DME it's seeing incredibly lean mixtures.

Try unplugging that sensor, and see what your scan-tool reads then.

Try swapping the two sensors, physically, from bank to bank, see if the weird voltage goes with the sensor, to the other bank. (Mark the "good" sensor first, so you don't get confused which is which. You may end up returning the other one for a replacement, under warranty, so don't mark that one).

[328 Power 04]

The early M54, and all E39 which run the MS43 dme use the normal narrow band zirconia sensors.
Only when M54 engine switched to MS45.1, that's when it went to wideband.

[aaronknotty]

They're 4 wire sensors for sure. Just running the stock Bosch 13477 for the pre cat. Yeah the interesting part was that one day when i lost the power, the mpg gauge shows about 8mpg (or pegged) when driving 15mph through my neighborhood haha looked up issues with that gauge, people said don't worry about it cause it useless. But, I felt it was pointing to an issue since the power loss. I fell like its basically just reading fuel mixing for its reding. I'll for sure do the smoke yes first. Sadly I just had to head for the UK for work and won't be back till mid December now! It's great! but kinda bummed cause I wanted to just fix the car. But I have a solid two weeks to work on it when i get home! swapping O2 sensors may be a good idea just to rule that out. I've run into my fair share of "impossible" tolerance before. I'm currently rounding up a smoke machine (made for cars haha) so I can hit it right when I get home.

As far as seal, the only thing I can think of that I changed (when i went from working fine to not working fine) was cleaning the idle air control valve and having to re-seat it. The little white extender tube didn't come out with it when i cleaned it. But it snapped back into place well. But also I like i said before if it was a pre-cylinder issue. I feel like it would affect both banks haha But i don't want to rule it out without testing cause "You Never Know"!

It very well could be that the engine is used to running rich by now haha The previous owner did tell me the can ran for a little with the camshaft position censor out, cause a previous tech forgot it (face palm...). How do these computers run as far as tuning? Do they take a while to calibrate? My previous Ford have to be re-set after a major change cause it would take quite a while to re-tune it self. Especially after a new sensor I'd have to erase it's memory but draining the computer caps (or just unhook it from the bat for a while). So could that be at play as well? If so, is there a special way to re-set the tuning parameters on a BMW?

IMG_9050.jpg

[aaronknotty]

Ok finally got back to work!

1. Ran two smoke tests and everything is leak proof. There is a small tiny crack in the idle air control boot. But not an open crack. New one is on its way none the less.

2. Opened the computer box. Someone tightened them way to hard and stripped them from the plastic case. So, that took a while and i JB Welded the nuts back into the plastic container. But checked the fuses in there and everything is good.

3. After getting a bit frustrated at not finding any issue. I decided to swap the O2 sensors and see if the issues follow either side. But I was doubtful due to the fact that it was acting this was before swapping the 02 sensor. But I decide to anyways. So to make my life a tiny bit easier, I pulled the plastic off the engine just just inspect more. After, looking at things and not finding any issues. I noticed the interesting ignition coil wires and how they ran into a long plastic housing. The housing had clips on it so i thought I'd pop it open to see what was inside. Well i popped one side off and noticed some resistors inside... And... the resistor is cracked in half! Now I don't know for sure if its the issue. But, I feel like its an issue. I would thing that that could be due to premature ignition coil failure the previous owner had. Also could even be adding to the issues that I have been facing. So I may try and see if i can track down another ignition coil wiring harness or if I can't. Replace the resistors inside.

Anyone else ever run into an issue like this?

(There’s a picture of the cracked resistor in the above post)

I did pull the harness and check resistance on all coil connectors. Getting 239ohms on each ground connector to chassis ground. So it seems the resistor should be fine. But not sure if it could possible be intermittent. I read another post we’re someone said they just do that with age but function properly. So could be back to the drawing board? Haha

[MarcoZandrini]

I’ve had the valve cover off the M54 engine in my E46 a bunch of times and I don’t remember seeing resistors anywhere. Do the wires and connectors look like factory stuff? What brands are the coils? They need to be either Bosch or Bremi. Anything else is suspect.

As noted the engine computer (DME) runs a rich fuel/air mixture until the coolant temperature reaches a specific value. The O2 sensors’ data are ignored during this timeframe. The weird O2 data could be a bad connector, a broken wire or a blown electronic component in the DME (Chris knows what a bad DME electronic component can do). I’d check the connector and continuity between the connector and the DME. If you’re feeling ambitious you can pull the DME cover and inspect it for signs of obviously bad components.

[aaronknotty]

Everything in the DME compartment looks great. Literally brand new looking with no signs of anything wrong. The resistor is inside the ignition coil harness. So you can't see it unless you poop the hones open.

I did have one other though last night though. When I cleaned the engine and the problem started. I'm curious if all the gloppy oil I cleaned off was hiding a valve cover gasket issue. Maybe by cleaning it, I exposed a bad install on the valve cover gasket. Which would make a little more sense to the new O2 sensor data i pulled yesterday. Cause now the issue isn't solely to sensor one (palm face).Theyre both reacting not but not proper.

I'm going to smoke the valve cover area locally today and see if thats an issue. If so, swap it and see if that fixed the issue.

Heres the O2 sensor data from yesterday. The flatline at the end is when i turned the car off i think.

O2 Sensor Bank 1.pngO2 Sensor Bank 2.pngO2 Sensor Bank 1&2, Sensor 1 .pngO2 Sensor Bank 1&2, Sensor 2 .png

[aaronknotty]

Here's a simple video showing the way that the MPG meter is acting up. Ever since everything started going south. When I brake now the meter drops to about 40mpg, pops back up to about 30mpg, then finally falls down. Ive read that there meters work off the mixture ratio/fuel trims. So does this point us in any other direction? Cause it be a vacuum thats causing that studded? I've smoked the thing lil the cows come home and still haven't found a thing haha

Also could there be an issue with the DISA valve maybe? When the issue started i pulled the valve to check for leaks and the o-ring was shot. So I replaced the O-ring, the flap and vacuum were working proper though. It would hold at about half open when I covered the vacuum hole. I did test to see what would happen unplugging the DISA valve connector during idle and there was no change, nor was there a change when driving around the block with it unplugged. Is it just a sensor for the electrical connector and everything is vacuum operated?

Also, I might swap out the o-rings on the "air distribution piece" Just to make sure thats no causing any issues either. Cause o-rings are cheap haha

Sorry trying to exhaust all options

[MarcoZandrini]

Ignor the mpg meter. How did you clean the engine? Did you use water under pressure?

[aaronknotty]

Well, I understand that the mpg meter is not there to be an accurate representation. It's just the way that its acting that is most likely pointing to the fact that there is an issue with how its reacting.

I noticed yesterday that the meter nulls at different point depending on how warm the engine is. When it's cold it nulls around 15, warming up around 20-30, warmed up fully nulls around 40. To me thats telling me that there's most likely a leak somewhere, thats closing up as the car warms up and giving me back some power. While staring to mix fuel a little more appropriately. Talked to a BMW tech yesterday actually and he told me the same thing when i told him what the car was doing.

As far as cleaning, it wasn't even that much cleaning even haha just some brake cleaner around where the dip stick goes in. Cause there was a lot of gunk and I wanted to clean it to make sure that a leak didn't come back or if it did i could tell where it was coming from. Then cleaned around the valve cover since there was some oil gunk ( same idea). Made sure not to spray any electronics in the process, nor vacuum lines (so i don't dry out the rubber. All in all I'm not fully certain the cleaning is was kicked everything off. Could have been wrong place at the wrong time kind of thing.

Though I did notice yesterday that there is a decent oil leak on the bottom of the car now. Which was not there before. Sadly my jack just took a crap on me and i can't get the car up high enough to get jack stands under the car. So, I might just take it to a euro shop and have them fix the leak underneath. Hopefully that will help with the issue. I did drive over a horribly small speed bump a few months back and scrape the bottom of the car. Very well could have screwed something up.

[MarcoZandrini]

A leak underneath could be the oil pan gasket. Replacing that requires supporting the engine, removing the engine subframe. Have the engine mounts replaced while the engine is being supported.

[bmwdirtracer]

I looked at the O2 sensor graphs, Aaron, and I really don't see a problem. There's no flat-line, there's no super-lean .004 voltage....so what are we chasing, besides the MPG meter? I can't determine what the bottom scale is - milliseconds?

The MPG meter is a funky thing, at best; i compares road speed to instantaneous fuel use to vacuum. If you want to see it read absurd numbers, coast down a long hill in gear. The video shows nothing of value - it's all under 20 mph, super low rpm, and looks perfectly normal to me. This gauge is meaningless at this sort of speed.

Your first post indicated cold-start misfires, then later they became cold misfires after 30-60 seconds? But they go away after a warm restart?

What are the codes which are PRESENTLY causing the CEL? How long does it take for the CEL to re-illuminate after you clear the codes?

[aaronknotty]

I looked at the O2 sensor graphs, Aaron, and I really don't see a problem. There's no flat-line, there's no super-lean .004 voltage....so what are we chasing, besides the MPG meter? I can't determine what the bottom scale is - milliseconds?

The MPG meter is a funky thing, at best; i compares road speed to instantaneous fuel use to vacuum. If you want to see it read absurd numbers, coast down a long hill in gear. The video shows nothing of value - it's all under 20 mph, super low rpm, and looks perfectly normal to me. This gauge is meaningless at this sort of speed.

Your first post indicated cold-start misfires, then later they became cold misfires after 30-60 seconds? But they go away after a warm restart?

What are the codes which are PRESENTLY causing the CEL? How long does it take for the CEL to re-illuminate after you clear the codes?

That is true. The data is different! That's why I said that both sensors look the same now. The data changed from what it was previously. Bringing into question, why the data has changed. The issues was probably not with the O2 sensor in the first place probably then. You know how these things go, some times an issue presents itself, making it look like the problem and may have not been the issue all along. So time to reset a little i guess.

Here is the current status or what wrong with the car:

1. Warm up issue is still present. Cold start, starts up fine. Then once the car goes into closed loop, the engine starts misfiring. Once the engine is warmed up, turn car off and restart. Everthing is good.

2. The car threw a cat under threshold code. At that point i checked the O2 sensor data and "bank 2, sensor 1" was flatlined and not showing anything different. Leading to investigating the O2 sensor circuit, and vacuum leaks in the intake. Though since it was only bank 2 messing up, that threw some flags.

At the same time that the cat code was triggered my mpg gauge started acting funny which is why Im bringing it up. I'm an engineer for a living and half of my job is troubleshooting(doesnt mean I know everything obviously haha, this is just standard troubleshooting procedure). I don't care what the gauge is telling me exactly. Only that its responding very different than it used to. The likeliness that the gauge goes haywire the same time a cat code triggers, and them being unrelated is very unlikely. So take it at that, I'm not relying on its information, as much as i am reading into the fact that its reacting to something else in the car. If it is road speed to instantaneous fuel use to vacuum that it's probably pointing to the fact that vacuum has changed in my system. Road speed is the same its always been when the gauge worked fine, so the other half of that equation (vacuum) is probably out of wack some how. Sorry to beat a dead horse maybe, there's also a direct loss of power since the gauge started wigging out as well. So, just too much of a side effect for me to fully dismiss. But, in the end it totally may be just random luck that the meter started acting weird haha If so, well dang.

3. After the last smoke test, the codes were reset again, and I'm taking it out for a drive later today. But the standard codes that always trigger after ever code reset normally are (usually fairly random on the cylinder thats misfiring):
P0313 (Misfire detected with low fuel)
P0300 (Random/Multiple Cylinder Misfire Detected)
P1353
P1342



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A leak underneath could be the oil pan gasket. Replacing that requires supporting the engine, removing the engine subframe. Have the engine mounts replaced while the engine is being supported.

Yeah good to know! Probably just have the euro shop down the road do that so I don't have to haha Thanks!