'76 450SL Idle
 

Ok... I'd just gotten used to the fact that my engine idles way too low and rough when it started to idle even lower... the tach doesn't even register that the engine is running! So I just keep one foot on the brake, one on the gas and go on with life... then all of a sudden from out of nowhere something in the car clicks and the idle goes to 1200 nice and smooth and strong! A few seconds later it clicks again and goes back to near death idle. Could this be the Idle air valve? If so... where is it and how do I test it? Any other solutions Definately welcome!!!!

Thanks!!