rough cold run 78 450sel
my 450sel 1978 has a rough running problem only on cold start engine fires up smooth then 5 seconds later rough run low rpms then after about 30 seconds of that engine speed increases to about 2000 rpm and doesn't slow down to engine is up to operating temp .. I have set timing made sure fuel delivery is adequate and clean tuned the car on a gas bench .. 1.5 % co 150ppm hc idle ,checked compression alright 125psi average nothing too varing from that.. I have the typical worn left side cam lobe I suspect that could be part of my problem when cold dead cylinder dragging along ?? I also checked engine vacuum when the car is cold 12 inches when the car is warm 15inches not so good or is it???? I know my 5.0 litre in my mustang pulls 18in right from start up and thats what a heathly v8 normally pulls right??? I also suspect the warm up regulator is not working properly is there a trouble shooting flow chart to diagnose it any help would be great . I also wonder what normal fuel econ is im getting about 8 miles to the gallon right now combined I expect a car to fly when it uses that much gas???