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Discussion Starter #1
While replacing the clutch and flywheel and having the exhaust removed, I thought it would be a good idea to change out the oxygen sensors on my E46 M3 that has 89,000 mi.

I got the four sensors on Amazon, which confirmed part fitment for each specific location. I'm pretty sure they're all Bosch...

I marked my plugs and I'm 99% sure that I plugged everything back the way it was without mixing up the sensors and connectors. I think they may even be keyed so that you can't plug them in incorrectly...

After putting the car together I was starting to have jerky acceleration. I figured this was because the battery was disconnected for close to 6 months and the ECU needed to relearn, but the problem got worse over time.

I am not getting any oxygen sensor error codes and I am using the torque app with the OBD scanner. sensor outputs seem to be doing what sensor outputs ought to do: line goes up, line goes down, sometimes it's flat... Those things have always been a work of Satan to me.

However, the engine runs at garbage, especially under load. I ran the tank down to a gallon and filled with fresh fuel. That didn't help either. I've checked my spark plugs. They're about 20,000 mi old and seem to be in perfect shape.

The codes have been getting are misfire cylinder x. And at random the x is whatever cylinder and eventually all of them. I don't need the ECU to tell me that... I've also seen pending codes of mixture too lean and mixture too rich, which seems schizophrenic.

I am starting to suspect that my new oxygen sensors are wrong somehow.

Thoughts?

Troubleshooting ideas?
 

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I think I responded to your post on facebook, but check the connections because postcat bank 1 has the same plug as precat bank 2.


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Discussion Starter #3
Mr Gizmo, my FB post got randomly taken down. I think a bug in their auto-blocking algorithm.

However, my saga continues. Your picture was very helpful and I was able to get the car up on the lift to double check all of the sensors. It did turn out that I although I had everything threaded into the pipes correctly, I did manage to reverse the two "A" connectors. I must have assumed that all of the plugs were unique and didn't pay attention. The sensors I got had extra slack in the cables so it was not readily obvious that I made the mistake.

I had hoped that this would be the solution, however it is not. The car was still throwing "too lean" and "too rich" errors along with "cylinder blah misfire", which would send it into limp mode. The most recent thing I tried was to disconnect all of the electrical plugs on all four of the sensors. My previous experience with OBD systems is that they use the O2 sensors for fine tuning and when the O2 sensors go bad, the ECU switches to a slightly rich base map, but generally continues to run decently. I was hoping that running with the O2 sensors disconnected would help me diagnose any potential problems with injectors or coils. However, the car is running like crap without the sensors connected. It is barely drivable, throws cylinder misfire codes and goes into limp mode. If I clear the codes and turn the car on and off everything works fine but within a few minutes, I can feel a misfire and then the car goes into limp mode again etc.

It seems like cylinder 4 misfire is usually the first reported and then most other reports are within the same second bank. I am guessing that the car detects misfires via a knock sensor, which is effectively a microphone, and therefore I misfire on cylinder number 4 might be getting detected on neighboring cylinders microphones...

My next step is to do a compression test on all cylinders to make sure that I have not developed a mechanical problem. after that I am thinking to swap the coil from #4 to #1 and see if the detected problem travels with it.

I'm really annoyed by these problems! The engine ran perfectly fine before I swapped the clutch. I am almost wondering if in the process I managed to knock some sort of a crank angle sensor that is messing with my ignition timing. That would explain a lot of things... But I would assume that the car is computer would be smart enough to figure out an ignition timing issue because the sensors are usually redundant between the crank and the cams with ECU's trained to look for an abnormal reading.

Again I don't have a super lot of experience with the E46 platform, so I don't know which sensors it has and how it interprets a different readings, or how dependent it is on having properly functioning O2 sensors.

People have suggested that my Amazon purchased Bosch sensors may not be correct for the car. Again in my experience the ECU uses the O2 sensors only for very fine fuel trim and only under cruise conditions. Previous platforms I've worked with all but ignored 02 readings at hard acceleration and hard acceleration is where I'm having most of my problems. However I'm not a believer in rebranded sensors being somehow magical. The platforms I've worked with before had very specific testing procedures with an ohm meter to determine whether the oxygen sensors were properly working. I could not find the detailed data for the E46, but I did test both of the heater wires and the sensor wires with an old meter before installing the sensors and they all came out very consistent.

Any technical help would be highly appreciated!
 

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Have you tried resetting adaptations?

Also, what happens when you first start the car from cold? When it's cold it runs open loop and does not use the o2 sensors (runs off base map) until it warms up and goes closed loop. Does it start misfiring right away? If so, clear codes, start it and see what codes set before it goes closed loop and throws o2 sensor codes. Might tell you what else is going on.

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Discussion Starter #5
Resetting Adaptors?? I would say no because I have no idea what this is. Details?

I don't know how much this ECU modifies its fuel maps between shutdown and startup. I've had cold startups that were very rough where the car would not even idle without me pressing the accelerator and keeping it alive. Then I can go in and clear all codes, turn off and turn on with things running a lot better, but still not perfect.

I'm waiting for the car to cool down now to do the compression test and swap the coils. I'm also thinking it might be a good idea to change out the fuel filter as I am certain that it has not been done and at least 50,000 mi... However, I would expect a fuel filter problem to be only evident under heavy load and I am having issues at idle as well as load.
 

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Do you have INPA or something that can reset adaptations? The car rarely runs perfectly so sometimes deviates from expected values by a certain % and it just says "this is the new norm, so I have to compensate by doing x" where x can be dumping more or less fuel, retarding timing, etc.

Compression test is supposed to be run on engine at operating temp.

And did you say you checked for vacuum leaks?


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Discussion Starter #7
Thank you for the compression test reminder and the specs. I'll get the coils loosened up and warm her up before doing the test. Also, I was going to look for a harness plug to kill the injectors during the test. Is there a fuse or a relay that would make my life easier?

Per the adaptations also a great point! We used to do this by disconnecting the battery and grounding a specific pin. I am using the Torque Android app with a bluetooth OBD sender. I don't think it has a way to reset the adaptations. I googled online and people are saying that there is a way to do it by playing with the key:


1: Place key in ignition and turn to detent 1 and count for 10 seconds ( only position 1 do not start the engine. )
2.Turn key back to 0 position and count for another 10 seconds
3. Now turn the key all the way to detent 3 to start the engine

2nd way:
1. Press pedal all the way to floor.
2. Put in key and go to position 2(do not start)
3. Wait 10 seconds.
4. Turn key back to position 0.(off)
5. Release pedal.

3rd way:
1. Put in key to position 2(do not start)
2. Press pedal to floor for 30 seconds.
3. Release pedal.

4. Start car.

I was going to try those later. When adaptations are reset, will I see the traction control light stay on? This happened after the battery was disconnected for over a week - the light stayed on until I drove about 300ft and the system regained trust with its wheel sensors. It would be great to have some definitive way of knowing if the adaptations were cleared.

Thank you for your help!
 

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For fuel, pull fuse 54 (2nd from left on the right half, bottom row, 20amp), then try to start the car and let it just die.

Never tried the reset method with a key, not sure what it will accomplish.

After adaptations are reset, no traction control light should not be on, they are completely separate.

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Discussion Starter #9
UPDATE: I think the problem is resolved!! As often is the case, there were a few issues happening, but the main culprit was so stupid, I almost don't want to admit it. I called a friend who had the INPA setup. As he was on his way, I examined the #4 coil and spark plug. Both looked OK, but on a hunch, I swapped the #4 and #1 coils. When my friend arrived within a second of looking under the hood, he noticed that my air intake boot was at a funny angle and upon closer investigation we discovered that the clamp was loose and the boot slipped off allowing the engine to suck un-metered air. (facepalm) It took 2 second to fix. He used INPA to reset the adaptations and the car ran better than ever. Upon warmup and hard acceleration, I once again got a sputter, SES Light and limp, but this time the code was, "Misfire Detected Cyl #1" - the misfire problem moved from #4 to #1 with the coil. Ordered a new Bosch coil online for $26. Should be here Monday. Everything else seems A-OK!
 

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Nice, yeah one of the other questions I had in one of the prior posts is vacuum leaks.

Sometimes you work on these cars doing something specific, end up knocking some sensor or clamp or hose unrelated and then chase them for days.



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