Owned since new this car has been serviced by Audi garages whole life now 180k. 5mths ago random misfires so replaced coil pack, spark plugs and leads and engine ran perfectly until just now with random intermittent misfires. Can start ok but misfires after 5 minutes or misfire on startup. If pushing on driving while misfiring between 10 to 20 minutes later engine runs perfectly again. Some days no misfires other days bloody awful. Recent VAG readings show misfires P0300, 0302, 0304, 0306 and P1394 - ignition output defective. Now leaning to replace coil pack again after fitting new battery. Can anyone add some possible causes here? I cannot detect any vacuum air leaks.

 

Hi, I have an A$ 1.8 B5 which misfires when hot up to 2400rpm then its ok? did you have any luck with yours?
Please help?

 

Dave, Suggest you get your OBD errors codes read. If Ignition Power Output Stage failures then replace the main coil pack. If Ignition circuit failures on a specific cylinder replace that ignition coil (sits atop each spark plug tube). In your case I would replace all the ignition coils in one go as a set.
I would also replace the ignition leads and spark plugs (after reading error codes) to eliminate them and if the car has done more than 60k's it would be a good move anyway.
A garage will read the codes for you and get them to reset after printing out.
In my case I finally found the cause to be Huco brand coil packs and after replacing with Bremi engine runs perfectly. This is after a number of months intermittent misfires and after replacing ignition leads and spark plugs and three coil packs.
One final note make sure you are getting the latest revision products from your supplier - I get mine from UK. And check web forums a google search on misfires for evidence of product failures or common causes/cures.
Hope this helps