Whats up all im new here, just picked up a 2000 a6 2.7 quattro ith 102k miles, the car was idling fine but under load it was bogging. I replaced the maf and cleared up the bogging under load but now I have a rough idle and throwing a p0300 random/multiple misfire code.. any ideas? plugs are new so is air filter and fuel filter.. any help would be great.

 

I should also mention I changed the battery, thats when the problems all started.

 

the 0300 group is more likley related to spark plugs/coils.
(example: 0303 - means you need to check cylinder no 3)
- You need to check your igniton coils/wires
- and/or you may have to do a throttle recalibration (not sure if that's done/needed on a 2000 after batery disconnect)
** by the same token:
- your MAF sensor maybe just started acting up - clean it
- Idle Control Valve may need to be cleaned/replaced

 

Funny you say cylinder 3.. It threw a p0303 so I put I new coil pack, started it up no codes and idles great.. Started driving then it started bogging again then the idle got rough and back to random misfire codes.. I'm thinking a bad ICM ?

 

It is entirely possible, of course, but I don't know if you can check it.
Fuel, spark, air - isn't that the triumvirate of proper operation?
Air: you replaced the air filter and cleaned the MAF (didn't notice that when I initially red your o.p.)
-
Spark: you replaced the plugs (are they the "right" ones?- these cars are finiky I think in terms of spark plugs) - proper torque?; you also replaced one coil...
I would say do a cheap investigation: get a spark checker ($ 7-8 at places like AZ, AA or O'Reillys) that plugs into the coil...that way you can check each coil and wire for appropriate electric arc
Since you said that the trouble started after replacing the battery, I wonder if you need to check your voltage regulator?!?
-
Fuel: you already replaced the filter. However, your last resort (after eliminating the first two categories) would probably be a fuel pressure check.
-
If anyone else can think of a more proper way to look at this, please chime in.

 

Well it gave me another cylinder 3 misfire after swaping coil.. this is what happened when the other icm wen't out.. I should have the new icm tomorrow hopefully that resolves it... should have just bought two last time.

 

FIXED! So I was running autolight double platinums.. Pulled one out and it was cracked and the rest had red soot.. Replaced them all with NGK iridium .32 gap.. Car runs great and pulls harder than I have ever felt it.

 

If anyone needs a ICM bosch 4A0 905 351 let me know since I already ordered it from the dealer and that wasn't the prob..

 

Excellent job.
So the spark plugs were responsible for the mischief
You can still buy that plug arc tester; in the future you'll diagnose the problem much faster and easier.