Cylinder 3 Misfire, Rear o2, SAI system

[SN95Audi87]

My Audi is starting to need some maintenance. I am at the 175k bracket now and I have few codes that need to be dealt with...I can't remember them on top of head but my secondary oxygen sensor is intermittent. I have secondary air injection problem, and cylinder misfire on #3. I recently tuned up my car by putting new spark plugs (copper - 0.28 gap) and it misfired for about 5 seconds then smoothed out. It did this twice, once on the initial install, and second on a cold day in spring a few months later. It didn't happen ever again and has been smooth. My question is can a bad rear oxygen sensor throw off readings that effect other systems in the car? Lastly, how long do coil packs last? I never changed them out and I owned the car for 6 years now. I did a service history report and they were replaced at 101-105k.


Nate

[VanCityA4Q]

Secondary O2 shouldn't affect other systems, it will just cause a cel but no loss in performance, coil packs can go whenever, try swapping coil 1 and 3 and see if the problem follows the coil, if it does, bingo replace it. For the SAI, get a blocking plate for the back of your head and just get rid of it. You can get a resistor from ECS tuning that will stop the code from happening, just plug it into the sensor wire for the sai.

[SN95Audi87]

Secondary O2 shouldn't affect other systems, it will just cause a cel but no loss in performance, coil packs can go whenever, try swapping coil 1 and 3 and see if the problem follows the coil, if it does, bingo replace it. For the SAI, get a blocking plate for the back of your head and just get rid of it. You can get a resistor from ECS tuning that will stop the code from happening, just plug it into the sensor wire for the sai.

Oh wow. Thanks for the info, I will go that route if the SAI becomes a pain in the a$$. It only misfired twice with in a few months time frame so I banking on that they are just getting old.