CEL's

[pnosker]

After driving home from Boston with a CEL on (It read as the Pre-cat O2 sensor), I started messing around with the water system and in the process noticed a bunch of dry-rotting vacuum hoses. I just replaced my Pre-cat sensor about a week before my Boston trip and I'm wondering why it's still going off. Any suggestions?

This thread is starting to become a jumble so stick with me please. After driving around today more CEL's went on. Scanning with my Peake reader, I got these codes: Pre-Cat O2 sensor (which I reset and went away for around 150 miles), Misfire detected, random or unknown cylinder (I suspect due to the bad vacuum lines which I ordered replacements for), Torque reduction: Transmission (Code 87). I have no idea what Torque reduction: Transmission means. I also have no idea why the code for pre-cat O2 keeps going off (twice since I replaced it). I suspect misfires are occurring due to bad vacuum. There's clear leakage on the hoses that feed into the injectors.

Speaking of hoses, I can't figure out what the part number of a certain hose is. Connected to the injectors are 4 hoses, one for each injector... the 4 hoses go into a black plastic device for splitting the air. The hose that runs to the black plastic splitter is what I need. See #2 in the diagram: http://www.realoem.com/bmw/showparts.do?model=CG73&mospid=47506&btnr=13_0416&hg=13&fg=15 (http://www.realoem.com/bmw/diagrams/h/i/8.png). I ordered #2 but need the hose that goes into #2.

[cooljess76]

Hey Patrick, I had a couple of misfire codes before and fixed them by replacing my flex boot between the MAF and the ASC valve. There were a bunch of cracks between the pleats in the rubber that I couldnt see when it was installed. A vacume line could also be a very likely culprit.

As for the O2 sensor, I'm assuming that you have OBDII and the code is for bank 1 sensor 1. There's a few things that could cause an O2 sensor to fail prematurely. If you're running too rich, or burning oil. Faulty wiring or a bad connection. Excessive moisture, leaking head gasket. Or the sensor may have been defective from the start. I'm know you're a pretty experienced mechanic and I'm sure you already know these things, but just in case you need a sensor for troubleshooting, I saved my old one. I replaced both of mine about a month ago. My precat sensor was fine, but it had a lot of miles on it. My post cat was the one that was bad and I tried to replace it with a Bosch universal, which didn't work. Shortly after I installed the universal, I got an o2 sensor heater code. So I replaced both sensors with Bosch OEM sensors. LMK if you need it and it's yours. Good Luck

[pnosker]

Well I got a new OEM replacement one (not universal... had the connector) which was cheaper than the universal and it appears to be working (I googled the problem and someone said the system might need a "hard reset"). My plugs are fine (I pulled them out) and it appears to not be running rich or lean so I don't think that my pre-cat sensor is foul after only 1000 miles or so. My flex boot is cracked which I will replace soon after I do the air hoses. Thanks for the offer on the sensor but if I need to I'll just bring it back to Autozone and get a replacement under warranty. I mostly need that part # for the hose that goes to #2 which I can't seem to find, and if anyone has experience with the Torque reduction code please advise. I guess it's possible that the vacuum line thing is screwing everything up (bad air causes O2 + misfire... possibly torque reduction too).