I recently replaced my failing alternator with a new one and found I had a smoother idle and more power at highway speeds. I put it down to having the right voltage and amperage when fixed giving me a stronger spark.Strangely the idle became really really smooth the whole way home after remaking connection.
as simple as that. Knowing what to look for is the tricky bit.Looking under the bonnet... Was 100km from Riyadh in a Disco heading for the southwest for a 10 day trip, and it just died. WTF?? Dont do this!!! Open the bonnet...12V supply to the coil had fallen off! Tightened the spade connector a little, never fell off again. Series 2 3.9 Disco with R380 - in hot climes these were upgraded (free) with a 120A alternator (bypassing the normal main fuse), and a mesh grille.