In May of this year I purchased a 2009 Audi A3 s-line with ~155,000Km on it.

About a week after the purchase, the CEL came on reporting cylinder 1 misfire. I started by replacing the coil followed by the spark plug with no change.

The problem has been getting worse from that point on with more frequent misfires and running rough.

By running rough, I mean that the car kind of shakes when accelerating. It feels like it's jerking to take off and then loosing power.

Now here's the odd part... this only occurs when the car is below its 90 degree running temperature. Literally this will occur right up to 89 degrees and the second it hits 90 it'll drive like a completely different car.
Additionally, it only occurs when running between about ~1500-2500 RPM. If I drive it down a gear or two it's fine but horrible for my fuel economy. A few times, I've continued to accelerate through the jerking and the ESP light will come on. After that, the car runs very rough until turning it off and back on again.

It's at the point where I cannot turn the car on and leave it idle without the CEL blinking reporting misfires... and only in cylinder 1.


The next step appears to be to open things up to replace the injector and possibly a carbon cleaning but I would prefer not to pay for that if I don't have to.

Any thoughts on the matter would be great and much appreciated.