E30 Zone

Had a bit of a problem earlier this evening. Was on a drive, car was behaving perfectly. Switched it off for 5 minutes, and when i turned it back on, the engine seems to misfire under load. It may not actually be a misfire, but sounds like it, and power has roughly halved. At idle the car is fine, and once at moderate speed is fine too.
I'm very confused, anyone else had a similar problem??
My car is an '88 325i
Help!

Certainly worth having a read through the archives here as there are lots of senarios...

Mine turned out to be a dodgy HT lead....

Hello mate,if you suspect maybe a high tension break down, pop the bonnet at night, my mates mazda 626 looked like the preverbial black pool alluminations when his king lead went..