Hey guys..I have a 2005 Audi A6 3.2 Quattro. When I bought the car from the dealer at the end of April, the sales man told me I'd be crazy to run premium gas in it web though that's what the manual states to run. My husband has ran mid-grade in it a few times. To be clear, there is an exhaust leak somewhere because when you take the black cover off the top of the engine you can smell it. My CEL came on not too long ago and nothing unburied was going on with the car. Took it to local parts store, got the code that was showing (P0430), they didn't clear it and it went away. The CEL comes and goes but now I have an engine shudder. The car starts fine, idles fine, and runs fine until it reaches the normal operating temperature. I read somewhere that a cold start could cause the CEL to come on but I usually allow it to warm up before taking off. We realized that we needed new tires so we put new tires on it and that didn't change anything. At first we thought that it was a vibration issue, & there was one but that's fixed after putting the tires on. Now we can hear the "shudder" better. Sometimes it sounds like there is metal to metal vibration but most of the time it's just the "shudder". It does this at all speeds. Could running the wrong gas have caused any of this and will running the correct gas plus fuel injection cleaner correct this over time? Or is this possibly a sensor that will need to be changed? Audi'a first response was the torque converter but that's a pretty costly job and we would like to start with the little things first. Should we take it to Audi and allow them to diagnose it or try replacing the O2 sensors/catalyst sensors before because I can't afford for Audi to replace parts that isn't going to fix it. Any help/answers are greatly appreciated! My husband is a mechanic and can do most of the work except pulling the engine/transmission.

 

P0430 could indicate that your driver's side catalytic converter could be bad. Your best bet would be to get your hands on VAG com and see what the measuring blocks are. If both O2 sensors parity each other then your cat is probably bad. if not, then one O2 sensor could be at fault.

A rough engine shudder could be related to cats not being warm, thus causing your car to more or less guess the right fuel to air mixture.

In either case, you could still change both o2 sensors AND the catalytic converter for less than a torque converter.

 

Thanks for the info! Where could we get one of those VAG coms? Do they rent those out at napa or anywhere?

 

Napa will not have it. You can visit ross-tech.com to buy the software, or search around on the forums here and see if anyone around you will let you use theirs to get the data you need. Without the right software on an Audi you will simply be throwing money at the car left and right until you finally swapped out the right part.

It's the best money I've spent on my 2.7T yet.