Once hot, engine surges between 400-900 rpm at a two-second period. When accelerating, valves make little noise and acceleration is sluggish. This never happens when cold. I checked for vacuum leaks, found none. From browsing related topics, I found that an Idle Speed Valve can be responcible or its regulator. I've heard MB dealers call it the Cold Start Valve/Ramp Valve/Throttle Valve. The dealer cost for the valve is $435 but when I ask for the voltage regulator noone knows what I am talking about?

Is there a VR for this valve & if yes, where is it located?

Thanks.

The idle speed actuator could be it. Start there but know it might not be the problem. We carry these in partsshop. Why use the dealer? They do not know what the part even is.

I have seen many idle speed control units fail at the same time because of too much amperage being pulled from the actuator.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM