When I got the car the biggest issue with it was the wiring. There were splices everywhere. Where there weren't splices the wires were stripping or just flat out split in two. This all needed to be remedied.
I wanted to spent a bit of time fixing up the wiring, as well as replacing the MFTS, Oil Pressure, and other sensors in the engine bay. This stemmed from and issue with the temperature readouts in the gauge cluster and further diagnostics which determined the MFTS was the problem.
The first order of business was figuring out what was causing the misfire. Turns out the ground for the oxygen sensor was not working. The reason? Well, the spade terminal had snapped off. That will usually cause that. I replaced it with a new terminal and voila, it was working. I will end up replacing this again in the future with a proper gauged wired and likely a more secured mounting location for the ground. I do not like where it is currently.
The diagnostics I followed to determine that the MFTS was a problem originated from this post which explained that I needed to do a series of built-in button-presses on the climate control unit in order to get the current temperature. If the temperature read a specific range of numbers then it meant the sensor was clearly not working. Turns out the reason was pretty simple, as seen in the pictures below. I ordered up a new plug from Germany and some replacement terminals and repaired the wire. Again, I will likely end up doing this again in the future in a more protective loom as the first rendition did not meet my expectations of professionalism.
The repair required two Audi repair wires which I used just for the wiring and pre-attached terminal. I was pretty unfamiliar with this type of terminal at the time. Some butt connectors and heatshrink and it was repaired.
Next up was the alternator wiring and oil temp sensor. This is definitely not stock. The ends on it were busted off and were simple spade terminals rather than the stock terminal. This will need to be fixed in the future as well, but for now I have spliced some new terminals onto it.
No, this was not my finest work. Frankly this was my first attempt and a great learning experience for me on how to and how not to splice, terminate, as well as insulate wiring.