[ab987]

Hey all,
Replaced my steering rack and cleaned my bank 1 downpipe (removed it and the O2) as I have a small oil leak from my turbo feed line (rein fitment issues). On the first drive, got 2C3D (oxygen sensor before catalytic converter, line fault) but upon logging it was normal. Cleared, didn't come back until mid way through the next drive. Turns out that as it gets up to temp now, it shoots to 26.98-27.10 AFR and kinda bounces around. Car throws the code and ignores the O2, trims go to 0. Car drives normally. I find it suspicious that after I messed with it, it just decided to commit suicide. Though it does have 97k on it. Anybody else experience this?

Thanks

[ab987]

A little update: Looks like the number it gets stuck on is arbitrary. I think it's the result of the ECU ignoring it that the reported lambda/AFR just ends up stuck at a value. Restarting the car (while driving or not) does allow the sensor to start reporting again, only to stop about 30 seconds later.

Is a line fault simply something like a quick short to ground? Maybe something internally is broken? Or could it be a connector/harness? Should I briefly swap the connectors for bank 1 and 2 and go for a low load drive around the block to see if it does it to bank 2? I'm charging up my INPA laptop and I'll watch the voltage tomorrow.

[Slade_]

Currently have a 2C9D code really messing with my car right now.
How is yours behaving at idle? Any misfires or stumbling?

[ab987]

Originally Posted by Slade_

Currently have a 2C9D code really messing with my car right now.
How is yours behaving at idle? Any misfires or stumbling?

It's acting perfectly normal, no stumbles or anything. I'm gonna monitor voltage soon. Do you have the same frozen AFR when it throws the code?

[Slade_]

Originally Posted by ab987

It's acting perfectly normal, no stumbles or anything. I'm gonna monitor voltage soon. Do you have the same frozen AFR when it throws the code?

I was scared to death of hydro locking the motor when I thought it was leaky injectors that I haven’t run it for more than a minute or 2. Will go ahead and check in a bit to see if I get frozen AFR now that I’m family confident its o2 related. Car is running very very rich.

Here is a video I took earlier today to give you an idea of what its doing at idle.
http://https://youtu.be/-QVNQBO0zoo

[Slade_]

Originally Posted by ab987

A little update: Looks like the number it gets stuck on is arbitrary. I think it's the result of the ECU ignoring it that the reported lambda/AFR just ends up stuck at a value. Restarting the car (while driving or not) does allow the sensor to start reporting again, only to stop about 30 seconds later.

Is a line fault simply something like a quick short to ground? Maybe something internally is broken? Or could it be a connector/harness? Should I briefly swap the connectors for bank 1 and 2 and go for a low load drive around the block to see if it does it to bank 2? I'm charging up my INPA laptop and I'll watch the voltage tomorrow.

A bad battery on these cars can really mess things up too..
definitely worth looking into.

[ab987]

Originally Posted by Slade_

A bad battery on these cars can really mess things up too..
definitely worth looking into.

That's something I hadn't thought of that's certainly possible. I did some logging with INPA and it reported the voltage of bank 1 pre-cat getting stuck at 3.07-3.09V when coming from coasting to idle. I've pretty much narrowed it down to that transition sticking to a voltage. I have a suspicion it's not actually sticking to this voltage but I don't have my multimeter for a while to test it, that could absolutely be some weird battery issue. Im gonna swap the O2s between the connectors and do a quick drive, and I'll update you if it follows the sensor or stays in the bank.

[Slade_]

Originally Posted by ab987

That's something I hadn't thought of that's certainly possible. I did some logging with INPA and it reported the voltage of bank 1 pre-cat getting stuck at 3.07-3.09V when coming from coasting to idle. I've pretty much narrowed it down to that transition sticking to a voltage. I have a suspicion it's not actually sticking to this voltage but I don't have my multimeter for a while to test it, that could absolutely be some weird battery issue. Im gonna swap the O2s between the connectors and do a quick drive, and I'll update you if it follows the sensor or stays in the bank.

Hope all goes well, looking forward to update

[ab987]

Originally Posted by Slade_

Hope all goes well, looking forward to update

I think it is a little too cold for swapped O2s given the rich nature of our cars. I couldn't get the motor to run for more than 15-20 seconds at a time without stalling out. Only way to know for sure would be to actually swap the O2s themselves, which of course involves lifting the car and I won't have my jack for another week. I guess this one will go down as inconclusive for now, let me know if your symptoms appear similar

[Slade_]

Originally Posted by ab987

I think it is a little too cold for swapped O2s given the rich nature of our cars. I couldn't get the motor to run for more than 15-20 seconds at a time without stalling out. Only way to know for sure would be to actually swap the O2s themselves, which of course involves lifting the car and I won't have my jack for another week. I guess this one will go down as inconclusive for now, let me know if your symptoms appear similar

Car is behaving a bit better once I reset adaptations.
Have not driven it due to immense amounts of smoke out of exhaust. Car boosts fine, its just a bit embarrassing

Codes popping up for me now are 29C codes for misfires on all bank 1 cylinders & this pesky 2C9D pre cat o2 sensor code.

Was going to send the car off to a shop tomorrow but decided to just raid FCP Euro and buy all the parts I need for a comprehensive DIY maintenance overhaul.

The car is currently leaking very badly from VC and Oil filter housing so all new gaskets and a serpentine belt kit are on the way. I also have both o2 sensors on order as well. Only thing I won’t do is intake cleaning.. will send her off for that.

The good thing about South Florida is that it’s always DIY weather.
I’ll be subscribing to your post and will keep you updated on my progress.

Our cars can be needy sometimes but when they run, they run

[Slade_]

Also, regarding your stalling condition.. are you 6mt as well?

My e93 is auto but when the battery was going it would give me a transmission fault and basically stall the car out.

Anyway, before I swapped out my spark plugs the car was literally un-driveable. I was only running it to make sure the motor swap was successful and didnt need any more work. It would stall at lights if I didn’t give it gas and around parking lots.. especially ones with speed bumps every 2 ***** feet. Didn’t help that the previous owner had maximum burbles turned on at stage 2+ with no MHD to reduce it. Imagine my face driving around police LOL

I’m sure you’ve done this but check your codes and see what cylinders are misfiring causing you to stall out. Consider getting new plugs or coils or maybe both. Once I changed my spark plugs, it was night and day. No more misfires and no more stalling.

I have brand new Delphi’s in my garage waiting for the maintenance party.

Let me know!

Edit: my e93 is auto and my fbo e92 is 6mt.. seemed a bit confusing

[ab987]

Originally Posted by Slade_

Also, regarding your stalling condition.. are you 6mt as well?

My e93 is auto but when the battery was going it would give me a transmission fault and basically stall the car out.

Anyway, before I swapped out my spark plugs the car was literally un-driveable. I was only running it to make sure the motor swap was successful and didnt need any more work. It would stall at lights if I didn’t give it gas and around parking lots.. especially ones with speed bumps every 2 ***** feet. Didn’t help that the previous owner had maximum burbles turned on at stage 2+ with no MHD to reduce it. Imagine my face driving around police LOL

I’m sure you’ve done this but check your codes and see what cylinders are misfiring causing you to stall out. Consider getting new plugs or coils or maybe both. Once I changed my spark plugs, it was night and day. No more misfires and no more stalling.

I have brand new Delphi’s in my garage waiting for the maintenance party.

Let me know!

Edit: my e93 is auto and my fbo e92 is 6mt.. seemed a bit confusing

Yeah it's a 6MT, it was stalling because I purposely had the O2s swapped between banks to try and rule out anything but sensors. It's run like that before (usually it notices and just ignores them) but this time around one bank would run richer and richer until it hit 10 "afr" on e52 (so like 7afr) and the other ran all the way to 26-27afr and the car would die.

[dpaul]

OP

If I have it straight - you removed bank 1 downpipe and "the O2" for cleaning and a bank 1 sensor-related code appeared immediately after re-assembly. I'll assume by "the O2" you mean the pre-cat O2 sensor. I'll further assume you mean you removed the sensor before removing the downpipe.

If so, the simplest possible explanation for your problem is that you damaged the sensor or its cable during the removal/installation. An intermittent connection could result in the symptoms you report. If the sensor cable is not disconnected before unscrewing the sensor from the downpipe and some care isn't taken, the cable can be subjected to enough twisting to damage it internally. This, I am somewhat embarrassed to say, has happened to me.

[ab987]

Originally Posted by dpaul

OP

If I have it straight - you removed bank 1 downpipe and "the O2" for cleaning and a bank 1 sensor-related code appeared immediately after re-assembly. I'll assume by "the O2" you mean the pre-cat O2 sensor. I'll further assume you mean you removed the sensor before removing the downpipe.

If so, the simplest possible explanation for your problem is that you damaged the sensor or its cable during the removal/installation. An intermittent connection could result in the symptoms you report. If the sensor cable is not disconnected before unscrewing the sensor from the downpipe and some care isn't taken, the cable can be subjected to enough twisting to damage it internally. This, I am somewhat embarrassed to say, has happened to me.

This sounds quite likely. I did not clean the sensor but removed the downpipe to clean some oil off of it, which required of course removing the pre-cat lambda sensor, and I generally do not disconnect the connectors but will in the future. I do think it is a cable issue like an intermittent internal short as you said. I've just never seen the voltage get stuck at a particular value before being restored to working condition after a simple restart (again maybe this is DME-related), working completely fine otherwise, and especially getting stuck almost always coming on-throttle. There seem like too many weird correlations going on.

[ab987]

Wanted to give a quick update because I did get around to replacing both O2s, problem is gone. I think @dpaul was right and I damaged the wiring when spinning it. From now on, it gets unplugged