Join Date: Dec 2002
Location: Doncaster, England
This is a bit of a long shot but is a recognised problem on modern cars.
It could well be an ignition coil problem. As the Alfa has one coil per cylinder if one had an intermittent problem it could result in stalling. This is because the ECU attempts to sustain the faulty coil. Back feeds to the ECU from the faulty coil cause it to momentarily switch off in an effort to protect itself from damage.
As the problem develops there will come a point when the engine will simply stop, and will have to be restarted using the key. Then once the coil fails completely the engine will resort to five-cylinder operation, and ironically will probably become smoother again.
Sorry for the long explanation but I got it out of a magazine.
Hope it is of some use to somebody.
1999 156 2.5 V6 SP3 Veloce Proteo Red 17" 15 Spoke White Alfa Alloys Eibach Pro Kit Springs/Dampers Powerflow Stainless Exhaust