just purchased 1989 740gl 2 weeks ago. was running perfect first week & a half and since then has been very hard to start, and once it starts, cannot touch the accelerator or it stalls. tough to start back up and when it does startback up vary rough idle until warmed up, then only slightly rourhidle. onced warmed up, starts right up. fair amount of black smoke,smell of raw fuel.replaced really bad spark plugs(really black) no difference.if ipartially disconnect 3/4 in. line off intake manifold by throttle body, idle picks up and engine runs like a top. car also has no fast idle when cold starting.