dimanche 4 juin 2017

O2 sensor problems

First of all, let me start by saying how incredibly indispensable this forum has been throughout the insane process of rebuilding this BMW.... There is seriously no word that exists to sum up the wealth of knowledge that you folks have. :bow:

For TLDR (Too long didn't read, jump to the bottom)

I've used all this info to fix and replace 50+ items on my 2002 325xi and have given this old girl a chance at a second life. That all being said, I'm really at a loss with what seems to be my final hurdle. I know people have feelings about aftermarket headers, and honestly, I would have just stayed factory if my O2 sensors weren't basically weather welded to the pipes / cat bungs. Neither I nor my local mechanic could get the old O2's out of the post cat section even with the entire header on the bench. Since I can't afford new header/cats, I bought aftermarket ebay headers.

After a bit of welding, the addition of a couple non-foulers, and two 90 degree elbows, the headers went on nicely and bolted up clean without any other modifications.

During this process, I put in 4 new O2 sensors. I didn't buy Bosch, but did get the non-universals that have the correct plugs for the car so I didn't do any cutting or splicing of wires. After everything was said and done and buttoned up, I plugged in the O2's. Now, I'm an idiot and didn't label anything prior to disconnecting so I did screw up here at first. The 4 wires coming from the computer are brown, red/white, black, and yellow. My O2's had white, white, black, gray. Because I was confused, I ended up plugging the car into itself and running it before I knew what was going on.

I have since traced all the wires, and thanks to this forum, also know that my cars wires are as follows:

Black - Negative Signal
Yellow - Positive Signal
Brown - Heater Element
Red/White - Heater Element

and that O2's common wire is the heater element, so in my case, white/white.

The new O2's are hooked up appropriately now (Though I still don't know which wire is bank1 and which is bank 2 for both post and pre cat).

I am receiving the following errors in INPA:

Lambda Probe Heater failure Pre-Cat Bank 1
Lambda Probe Heater failure Pre-Cat Bank 2
Lambda Probe Heater failure Post-Cat Bank 1
Lambda Probe Heater failure Post-Cat Bank 2

Along with this I'm having a very rough idle that develops which then throws the following additional errors:

Burning Fail Cylinder 5
Burning Fail Cylinder 3
Burning Fail Cylinder 6
Burning Fail Cylinder 4
Burning Fail Cylinder 2

The INPA F5 - F7 Rough readings once this develops are way into the red. If I turn the car off, and on, OR if I clear the codes, the rough idle goes away for 5-10 minutes, and then it repeats this process.

If I run without the O2's plugged in at all, I get a pretty clean idle along with and smooth running.

I went to Autozone and purchased OE replacement Bosch O2 sensors for testing.
At this point I pulled out the multimeter for some readings and got the following:

Car running, Pre Cat harnesses read 13v across the heater element wires brown and white/red.
Car running, Post Cat Harnesses readings bounce all over the place, 0.00, 0.1837, 1.5321, 0.00, 13.384, etc, etc.
Measuring resistance across the brand new O2 sensor heater wires (White/White) I get either 0ohms or 0.L

If I have the O2's plugged in and start the car, the Pre-Cat gets hot instantly as it should, the Post never do.

On top of all this, if I open up INPA and read the lambda sensor values, I'm not seeing accurate readings at all. For example, if I only have one post cat O2 sensor plugged in, all 4 heater element readings in INPA show 99%+. That's the same reading for a wire that's plugged into nothing as it is for a wire plugged into a brand new O2 sensor. I would expect the ones with nothing plugged in to show 0%.

So, to summarize or TLDR

****TLDR****

After header install, I'm getting rough idle and O2 Heater errors on all 4.
Plugged car into itself for a bit (Pre-cat wires from harness plugged into post-cat wires from harness) not sure if this can fry the computer or what.
2 Brand new Bosch brand OE O2 sensors for testing. These aren't installed in the pipes, just loose.
Strange power readings on pre-cat heater wires.
Strange INPA readings.
I'm not looking at actual O2 readings for anything yet since I can't get passed the Heater element errors.

I don't even know what else to test/check at this point.

One thing I just remembered as well is that after the header install when I first started the car, we saw some arcing from one of the post cat sensors to the heat shield so I'm not sure if that could have killed something.

Any help would be greatly appreciated as I'm at a complete loss. :banghead:

Thanks!!


O2 sensor problems

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