Engine surging at all RPMs

[91 SL500]

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

[iwrock]

I am not 100% sure of the problem, but check here. That is essentially the same engine, with just about the same problem you are having. The 400E has the same kM119, but different displacement. Hope that helps.