Hello. Have a 850er, 2.5 L, 20Ventiler and the following problem: 3 weeks ago he ran only on 4 pots. New spark plugs (Volvo), new distributor runner and cap (Bosch) and discovered during removal that a spark plug at the lower edge of the insulator was broken. After the replacement he purred like a kitten. After 1500 km only on 4 cylinders again, this time the first does not run with. Spark plug was completely added, other candle and ignition cable from my part carrier was converted, no change. Ignition coil can’t really be when only one cylinder strikes? Distribution cap and runners look good, kei crack, nothing loose…. Does anyone have an idea?