thanks for the advice. i did find one more vacuum line that was in miserable condition and will be dedicating a day to do nothing but trace and replace vacuum lines and hoses. it seems like those braided fabric ones kind of disintegrate from the outside in. layers just peeling away. with the two i mentioned, you can feel the air pulsing through the lines if you touch them.

best as i can figure, the IGNITION CONTROL MODULE nearest the firewall is responsible for the 2,3,and 6 cylinders and the module closest to the front of the vehicle controls cylinders 1,4, and 5. not what i would have expected but seems to be how it is.

from all the reading and and scanning that ive done in the last couple of days, it seems the lesson to take from this is if you get a code for misfire cylinder 2, replace the icm nearest the firewall, if you get a code for misfire cylinder 5, replace the icm closest to the front. 90% of the time this will solve the problem

the longer i ran the car with the misfires, more and more codes popped. every time i cleared them and ran the car, the same codes popped and always in the same succession:

p0300 random multiple misfire

p0302 cylinder 2 misfire detected

p0306 cylinder 6 misfire detected

p0303 cylinder 3 misfire detected

then if i went a good while without clearing the codes i would eventually get a code for an o2 sensor. i cant recall offhand what it was but i think it was something about an intermittent prob with one of them.


my best guess is that there is a chain of events that occurs. if you drive the car with a problem, then the car compensates and another problem occurs and this goes on and forms a cascade until failure. or driving it with a problem taxed the car and caused another problem to occur which taxed the vehicle more causing another problem and so on until failure. fix the cause of the original problem, clear the codes and drive it for 10 - 20 miles so the car can adjust to the new (repaired) conditions, and all goes back to normal. hopefully.

 

Bringing up this post.
I own 2003 a6 with ASN engine.
Having trouble with p0300, p0306,p0305,p0304
So cylinder 4,5,6 are misfiring. cylinder 6 is ALOT more worse than other.
I've changed spark plugs, chaned coils. Tried even 1.8t engine coils. no effect. always same codes same cylinder.
I dissasembled the head and cams look perfectly fine. like brand new.
Car starts up fine and has power no issue. When rpm's closer to 2k, then engine fault light starts blinking.
I feel no misfire when driving.
When idle, I can feel the misfire.

What can I do what can I check? I attached few pictures from live data. maybe someone can help me?