S929

Here's the problem, 2005 Audi A6 error code P0305 misfire on cylinder #5 The misfire is noticeable first thing in the morning when you start the car which goes away after 30 seconds or so and under hard acceleration which will cause the check engine light to flash. What I've done so far, I have change out the spark plug and ignition coil with new parts. No change, still have the problem. Anyone else had this issue that was caused by something other than the coil or spark plug?

BernieBenz

Are you also getting a random misfire code, in addition to one for a specific cylinder?
Had the random misfire codes on my '02 2.7T APB several years ago after changing plugs, Had changed to a Bosch 4 ground pin plug, Returned those plugs for the Bosch OE Iridium 9607 (FR7D1133X). Solved the problem, great plugs!

oaktreelimb

I would check and clean all intake valves. When you are there cleaning intake valve, I would replace injector #5 too.

xroadrashx911

Sounds like you might need the carbon deposit cleaning. I had the same issue, luckily it was only a bad spark plug on cylinder #5. I did change the coil packs too. Here is a link to the cleaning job... good luck...
https://www.audiworld.com/forums/a6-...clean-2764902/

bigbruggsy

Hi all, just an update, I drained the motor of its all and water and oil came out. No metal parts, but I'm guessing at least that the car suffered from major head gasket failure and then piston ? Valve failure? Or is that part of the head gasket you can see in the photos?

Tutts

Had the same type of cylinder misfires when cold for about 20 seconds. Also had O2 sensor rich codes. Audi mechanic said the fuel injectors on these 3.2L motors are known for leaking into the cylinders after the car sits overnight. I did the intake carbon cleaning process and at the same time replaced the injectors based on what the mechanic said. Cold misfires are now a thing of the past. I replaced all 6 injectors on spec and the car runs great now.