Today I was driving and my 2002 Audi a4 1.8t check engine light came on, so I went to my closest advance and had them check the code and it came back for the car converter. My car has been running sluggish when I accelerate at the beginning after once I'm going it's not bad tho, should I just replace the cat. And hopefully that should fix it? I was considering going with a downpipe possibly if that would be better need some suggestions on how to fix this. It's an automatic but it's a sports shift it doesn't run as rough. Any info would help thanks!

 

You have dirty/oily Oxygen Sensor. Don't replace the cats at all. Go to Wallmart or Can Tire and buy Cat Converter cleaner, or Penzoil Fuel Injection Cleaner. Add to gas 3 times and your cats will be cleaned. Also avoid Shell gas as they add some lubricant to it that stays in your exhaust.
Go to Esso or Petro Can for the next 3 fuel ups. Don't expect the change right away as removing oil from Exhaust Pipe will take at least 1000km. Also avoid being stuck in traffic, and change your route to work to highway.

 

Alright I will do that as soon as possibe. Now once I have done this will my CEL light just go off or will I need to take it to a shop to get this fixed? And once it is correctly cleaned my car should stop running so sluggish correct? And I will def avoid shell gas, also should I maybe run a few tanks of high grade gas during the injector cleaning process? Any ideas are welcome and appreciated greatly!!!

 

This is typical for dirty Oxygen Sensor that the car runs well on high RPMs, and is sluggish on low RPMs, because the air/fuel mixture is not measured exactly at high speed. You should always use high octane fuel on an AUDI. Once O2 sensor is cleaned everything will come to order again, yet it will take one to two weeks.

 

Alright awesome I will give this a try start running higher octane gas and go ahead and run injector cleaner through it as well hope this works wiill keep you posted on if it clears up and a week or so thanks for all the advice!