hello everyone !!! i"m a machanic work out at home , i do alots of work on late model BMW & MERCEDES , so far i fix two sl 300;500 with exact same problems as you guys posted here after these cars went in and out of other shop end up with a longs list of replacement parts i mean all of ignt & fuel except it fuel injector, finally come to me , here what i found the cars would start & run fine when it cold but when it getting warm up it start to run rought like miss fire , will not moved like it should when speed 5 to 15 MPH @ 1k to 2k RPM unless you give it alots of gas at the padal then for a split second delay it woke up and jump , for hight speed no problem , another things after it run hot you shut it down for 5 min or so , will take a fews crank to start up and smell like raw gas . btw forgot to mention both of these cars got there fuel injectors clean by injectors shop with professonal machine . if all of the above sound like your problems , replace all injectors and seal , the cause is these injector or injectors only leak down when hot (matal on injectors check valve expanted due to heat) make your engine run idle with too much gas (rich) ,after hot shut down it leak down to your intake cause hard to start . hoped this will help some of you guys before spend too much money.

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luan