Replaced water pump, now idle is fluctuating...

[suginami]

I had the water pump replaced yesterday - it went out while I was on the freeway.

I have a 1993 300E, with the 3.2 liter M104 engine, 134,000 miles on the clock.

Had it replaced by my MB indie, and when I pick up the car, the idle is fluctuating up and down. It wasn't doing this when I brought it in. It does this at idle in any gear - park, drive, reverse.

The check engine light is not on.

I don't know if there is a connection between replacing a water pump, and a fluctuating idle. Is there anything they could have touched or disconnected that could have caused this?

It "feels" like a vacum problem, so we checked to make sure all of the vacum lines were connected. They are.

Is it the mass air sensor?
Is it the throttle actuator?

Wouldn't these trip the Check Engine Light?

Is it just an amazing coincidence that immediately upon changing the water pump, I get the failure of another component?

Heeeeeelp.