OPEL Corsa Lite problem

[Xperia]

I have an issue with our 2008 Corsa Lite. A week ago it went in for a minor service. On collection I noticed the engine management light flickering (fast, irregular) at low RPM (disappears at higher RPM). I spoke with the mechanic and he said he hadn't noticed it during the service or test drive but it had occurred after the car wash. They couldn't sort it out at the time so we booked the car in again for tomorrow. On Saturday however one of the cylinders went dead and the flickering light disappeared so I took it back to them this morning. They state now that one the coil is faulty. Replacing the coil gets all cylinders working again, but that flickering light is back as well. They are busy checking the electrics and alternator but don't seem to have any clue yet what the problem could be. 2 other points I should mention is that left rear light bulb fuses shortly after replacement and car idle is very rough.
Any advice will be appreciated.

 

[Rickster]

Did they wash the engine during the service?

 

[psion]

Replace the coil leads too, they tend to start arcing to the head after a while. Start the car in the dark and you will clearly see if the coil leads are arcing.

 

[Howl]

I had the same problem. New battery, two alternators, one distributor and two sets of spark plugs. Apparently what fixed it was a loose earth wire.