Please help! 2000 A4 Avant 1.8T problem [Archive] - Audi Forums

: Please help! 2000 A4 Avant 1.8T problem

08-12-2011, 06:03 AM
Hi everyone
I need advice. My audi's CAT cracked near the outlet manifold. I had it welded and since then, whenever I drive in a high gear (high revs) and select neutral, the engine cuts out. I can then either select a gear again and it restarts from a running start, or I can restart it by means of ignition. I went to a service center that has a computer and their comp says there is an error at the 1st O2 sensor. Something like bank 1 or something. They then reset it and the error was cleared. It happened again and I took it back to the service center and the error had returned. Is it possible that the person who welded the CAT might have damaged (fried) the O2 sensor? Or is that not possible. May it be the sensor that is just faulty? Or does an O2 sensor fail completely and not intermittently. Every mechanic tells me a different story and tells me to replace a different part. Some say I cant weld a CAT because it then has uneven heat at that section and makes the sensor pick up a fault. Others say the sensor must be replaced. What should I do? A new BOSCH sensor costs R725.00. I can't replace it at that price not knowing if that is the problem. Please help. Thanks. Csuperc

08-13-2011, 04:11 PM
Drive the car and the pop the hood and have a look at the turbo and see if its glowing red.

If it is the CAT has collapsed if not then it may be that when he welded the CAT he killed the sensor or it still cracked.

If I was you I would swap it out and get a sport CAT checkout 034.

08-15-2011, 12:52 PM
howsit man, thanks for taking the time to answer some questions. I spoke to the people who welded the CAT and they said they checked the inside of the CAT and it was still perfect (not cloged up or collapsed). I think they would have told me if it was. Also when the CAT was broken it was not just cracked, it was completely broken off at the outlet manifold. While it was cracked (in the process of breaking off completely) I didnt notice the car deing at all. Also the computer says its a O2 sensor fault so surely its not the CAT thats still cracked, because when it was confirmed to be cracked there was no problem with the car. Ill check the turbo to see if its glowing red after a drive.