that_tg

I am at the end of my rope with this car (97 A8). It has a misfire on #4 and I have done everything I found here that makes sense to me.

Moved coil. fail #4
Moved plugs. fail #4
Moved and cleaned fuel injectors. fail #4

What am I missing.

I can hear the injector working with a screwdriver held to it. When you start the car it takes a little time to throw a misfire code.

Any help would be great.

haggisuk

Maybe get more info in D2 section, but is there not a pair of ignition amplifiers on the d2 or am I thnking of something else.

If there is swap them and see if the misfire moves

MP4.2+6.0

It's a D2 so try there (or C5 A6 4.2 for basically same set up). Besides injector, at some point consider maybe the knock sensor itself is no good, unless that is you also feel the misfire. And if you do, could ultimately be the ECU has gone bad. Broken or tired electrical connector at coil pack would be yet one more, and a lot cheaper than ECU.

that_tg

So sorry!

tenspeed

Pistons, rings, valves, gaskets? A compression test should tell you if the cylinder is healthy.

SS_RTR

You mentioned "moved plugs" but I know from recent experience that moving a plug vs a new plug made a difference for me. I was just about to remove the intake to replace injector but decided to install the new plug first. I had already swapped the plug with a plug in another cylinder, but misfire stayed with the cylinder. If you haven't tried a new plug, it may be worth a shot.