300CE nasty idle

[Gerard]

Hi All,

I know this is a well flogged problem and I have done many searches here, but I dont think I've seen the exact same symptoms as mine.

1 The cars starts great and warms up perfectly.
2 After about 15 mins a little miss (like off a cylinder) starts to occur,
3 by 30-35 mins its quite bad, the engine idles really rough (especially in D), just about manages to accelerate, once off idle, its fine,
4 then after about an hour of running, the miss is gone and wont return till the next time I drive it. The same happens each time.

M103, 180,000miles.

Any ideas? Thanks in advance
Gerard