Join Date: Apr 2007
Location: Maidstone, Kent
Re: Bed-time reading??
Smoke from the exhaust can mean lots of things. However, it does seem to indicate a cat problem, especially considering what the manual said about the flashing light. The diagnostic system should be able to detect a cat problem though, so I wonder why its not being reported (unless alfa's implementation doesn't detect this?)
The misfiring could be caused by spark-plug fouling, so its a good bet to get them looked at. In this case, its likely that a significant amount of unburned fuel is making its way to the cat, which can seriously damage its operation due to excessive temperature (you can tap the cat to get an idea if its damaged, if there is a lot of rattling coming from inside then its likely that it is damaged.) Although I'm not sure that smoke is an indicator of this kind of damage.
I'm pretty sure a garage would be able to check the functioning of the coil and its ability to operate the plugs, so its worth testing if they can but maybe not insisting that it's replaced.
I'm no expert mind you, but I think your looking in the right direction with the plugs. Other thing I can think of is burned exhaust valve, which would also release unburned fuel into the exhaust system.
Hope that helps a bit...