Thread: 3.9l Engine missing when coasting

Hi l have 1990 range Rover classic 3.9 injected Not being used a huge amount at the moment doing a rolling resto on it. Rebuilt front and rear calipers fitted a new master cylinder and fitted new flexible hoses and had the distributor rebuilt and re-curved from a very reputable well-known specialist. The advance system was seized
Fitted the dizzy and took it for a few drives. Drove great ( the recurve woke up the engine)hasn’t been on the road for awhile but yes it’s got fresh fuel in it. Accelerates well pulls hard under load But when coasting (sitting on a constant speed) it Coughs and splatters to the point that it almost dies on me. Starts up beautifully revs Freely, no coughs or missing at all. I think it might be running rich burning the fuel on acceleration but when cruising it’s getting too much fuel? Where do I start? Any help? Would be muchly appreciated. Also, I’m new to the site so having trouble navigating around at the moment so if this Fault has been diagnosed in a different post. I’m sorry still learning

Could also be a vacuum leak, and two things have been disturbed that rely on vacuum, the distributor which uses vacuum to advance the timing, and the vacuum assisted brake cylinder.