SL500 surging at all speeds
 

I need some advise. I have a 91 Sl500 that has been surging at any speed and RPM. The engine RPM falls to about 400 then jumps back to about 1000 in park. I can hear a clicking noise under the engine cover that is in sync with the surging. I took it to the dealer and they said it was the fuel computer causing the problem. The bill for that is going to be $1900.00. So, as you can see, I sure would like to get your input before taking out a second on the house to pay for car repairs.

I don't know what a fuel computer is, but the throttle actuator is one of the likely causes of an idle surging like you describe, and the part probably runs in the $1,500 - $1,700 range, so that might be what they are replacing.

Is the check engine light on? I would read codes from the 38 pin diagnostic module, specifically pins 4, 7, 8, and 19 to see if any codes have been stored that might give you a clue.