[s-cars] S6 down with bad misfire (again)

[ACD]

First time around I thought I had a bad tank of gas: light misfire that would desapear and come back in a day or two. It got worse quickly and I began my search for culprits. After reading all the available tips I discarded POS failure and declared #4 ignition coil officialy dead. After I replaced the problem seemed to be gone... for 10 miles. I popped the hood again e began playing with POS and connectors, and cleaned the connectors with fine sandpaper. Problem was finally gone. If coil was the problem, why ithe misfire returned 20 minutes after replacing it? And why it went away after cleaning the contacts? Dirts could be causing intermittent misfire? Very strange...

Two months of pure joy went by and - you guessed it - same thing happened again. I disconnected injetors one by one, problem was located at cylinder #3. I swapped the POS, no change. Checked the spark on plug: on first try, OK. Five minutes later, no spark. Nothing. 

I've been driving my car hard on the road - no track work -  and temperature here is always between 80-90F. I can feel the heat coming from the engine bay thru the vent system. FMIC is on the way, hope it helps to control all this heat. Also will work on the heat sink and extra ventilation for POS. A simple flexible plastic hose with a filter to avoid water should do it. We can also connect the hose to a heat sink and cool the POS indirectly, avoiding moisture. I'll post whatever I come up with.

I'm still investigating before replacing another ignition coil. Suggestions are welcomed.

Antonio