The cold start valve is at the front of the intake manifold - you can follow the line from the fuel distributor to it. There are two wires that go to it as well.

The warm-up compensator is on the left rear of the block under the intake manifold. Hard to see from the top.

The idle air valve and auxiliary air valve are under the intake manifold near the from of the engine.

I would guess that your problem, though, is fuel injector or fuel distributor related, or maybe a vacuum leak.

Does it happen when the engine is hot, or cold?

If you send me an email, I will send you an overview of the injection system.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe