My 85 500sel dies at times when slowing down or just sitting Idling. Also when idling cold it runs at around 600-700rpms, but as the engine warms up it progresses to around 1100-1200rpms. Other than that the car runs, and accelerates perfectly. I have switched out three different Idle Speed Control Units and find that only one with send voltage to the Idle Speed Control Valve when starting up, but it kills the engine (every time) within a second of starting. The other two ISCUs will let the car start and run, but as stated above, engines dies at times.

I have done research on this issue and apparently there are three "transistors" that cause the issue I am having, but even though I watched a YouTube video on the problem transistors that need replacing it was not made clear by the person exactly which three transistors need replacement. He said you could Google for a electronic schematic of the ISCU to troubleshoot for the bad transistors but I could not find the electronic schematic I need so I can fix these ISCUs. ANY help would be greatly appreciated,. thank you.

I have marked in "RED" three (three leg) transistors that may be the ones the video was referencing, but only because the person that did the video did at one point mention a 3-leg transistor.

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