03 S6 cold weather issues

[Castor Troy]

As we're approaching winter, I'm reminded that last year my S6 ran into some pretty bad issues in cold weather, and the colder it gets, the worse it gets.

Around 40F, on initial startup I get a single cylinder miss. Even after the engine is warmed up, the miss continues. The only way to get the miss to go away is to turn the engine off and back on. I haven't had a chance to throw VCDS on to see what cyl is missing, but it is on my list.

As the temperature gets colder, it gets worse. Last year on a day that was -20F, I had to start the engine with the pedal halfway to the floor and hold it at about 1800RPM for a minute just to get it to idle, and I'd guess I was down 2-3 cylinders. After I'd driven few miles, I turned the engine off and back on, and the miss was gone.

Any thoughts as to what would cause this miss? My car has a 6 speed swap with a Daz tune, and has been converted to R8 coilpacks. Is it possible that this is due to the coilpacks?

[rollerton]

It's hard to say what the problem is- I assume you get a CEL with the cold start problem?
You might try the variables that rely on temperature like the coolant temp sensor, maybe? the MAF. I can't easily relate any of the ignition parts to temperature, and if anything they'd likely have more problems when its very hot than cold. Maybe there's a fuel problem/ injectors freezing at that temp?
if it's misfiring and then goes away after a little heat is generated then fuel could also be involved..

[BlackOnBlackA6]

I'm not sure what would cause it, but 2 months ago I had something similar and my mechanics thought it was two cool packs, but found two of my spark plugs were gapped at .42 instead of the 0.32 where I gapped it almost a year ago. He couldn't explain how it stretched to that, but....

Good luck finding the source