Hello All ! I am a new member joiining in this forum. Up to now, I haven't found clear answers on what to do with the following fault codes. Can anyone help ? Got a 2001 A4 2.8 quattro.
-----------------------------------------------------------
16804 - Catalyst System: Bank 1: Efficiency Below Threshold
P0420 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16685 - Cylinder 1 Misfire Detected
P0301 - 35-10 - - - Intermittent
16688 - Cylinder 4 Misfire Detected
P0304 - 35-10 - - - Intermittent
17953 - Throttle Valve Controller: Malfunction
P1545 - 35-10 - - - Intermittent
-----------------------------------------------------------
From these codes, should I:

1. Change Ignition Coil and cables ? I already changed them 6 months ago
2. Change Alternator? What brand is most recommended?
3. Clean fuel injectors with a special product?
4. Change spark plugs?
5. Perform a Throttle Body Alignment?
6. Replace one faulty Oxygen sensor? I changed Right and Left Cats 6 months ago

Thanks for any help

 

check your plugs first. the 2.8 hardly misfires. if it's not the plugs, i change the wires from one cylinder to another and see if the misfire follows. if it doesn't it's the coils

 

yea change the plugs, then look into that throttle body problem.

 

Thanks to Trey25 and hiwords.

Following your recommendations I ordered some new spark plugs. I chose BOSCH Spark Plug Platinum+4 since a lot of people are giving good comments about those. When installed and after a couple of weeks, I will send an update on the misfire problems. Will try swapping the wires if problem persists.

I found an article about the cleaning of the Throttle Body on AudiWorld Tech Articles: http://www.audiworld.com/tech/eng.html

 

ya those are the plugs i'm using. holding up pretty well. for the throttle body, just get some throttle body cleaner and then spray it into the hard plastic piping that leads to the throttle body. you dont' want to take that pipe off. then let it soak for a 5 min then start the engine. do it a couple of time because you might not have gotten everything the first time. it'll be a little hard to start it at first but let it crank, and don't spray too much lol.