I own a 1986 300 SEL 6 door limousine that has recently started behaving in
a peculiar way. When I start the car the idle is very rough and when I put
it in drive it feels very sluggish. I can floor it but there is only very
slow acceleration. The car feels like it drives only on 5 cilinders. But
when the engine reaches about 2000 RPM the 6th cilinder kicks in and the car
behaves like it should. Also the economy meter shows hightened fuel use
until the 6th cilinder kicks in. When driving it is very slow on the road
and then around 2000 rpm it suddenly drives normal and I can attain higher
speeds normally. When I slow down it starts all over again.
Could it have anything to do with the spark plugs or the spark plug cable?