Engine continuously surging on cold start up

[Equitas]

When I start my car cold, I find that the engine revs up (higher than a normal warm idle -- perfectly normal) but then drops down to a normal low idle (perfectly acceptable) BUT THEN CYCLES and does it again, and again, and again....each time the cycle shortens until it is reving at the normal warm engine idle speed. It doesn't sound normal.

What does this indicate? Sounds like there is a problem with my cold idle thingy. Is it the thingy, and if so, what is the thingy called and what should I do about it?

[Graham]

Originally Posted by Equitas

When I start my car cold, I find that the engine revs up (higher than a normal warm idle -- perfectly normal) but then drops down to a normal low idle (perfectly acceptable) BUT THEN CYCLES and does it again, and again, and again....each time the cycle shortens until it is reving at the normal warm engine idle speed. It doesn't sound normal.

What does this indicate? Sounds like there is a problem with my cold idle thingy. Is it the thingy, and if so, what is the thingy called and what should I do about it?

Sounds like the usual D-Jet cycling caused by the 1500rpm idle cut out. But is this a D-Jet - I don't know these models well and seem to recall that 280SE had both a 6-cyl M130 and an 8 cyl M116/7 engine at about that time.

If it is the D-Jet V-8, cycling indicates a vacuum leak. It could be external or it could be the Aux Air valve (AAV) sticking open . You can check this by squeezing or removing and blocking the el shaped hose from the AAV to the idle valve right at the front of the engine. Replacing the AAV is a bit exppensive, but it can be cleaned as a start (Do a search here for AAV) Also check all vacuum connections. We can supply a list if need be.

You could also try adjusting the idle speed by screwing in the idle screw (Big slotted head, just to right of above el hose). If you can screw this all the way in without stalling the engine, then you have a vacuum leak somewhere.

PS: If you need help, you might try Arthur at Eurocars - located on Algie Ave in Etobicoke. He knows the D-Jet as well as Mercedes in general.

[meltedpanda]

My thoughts exactly Graham, but then again you gave me all of mine LOL