Engine revs high and then low when starting?

after changing a leaking hose (feeds radiator fluid but the hose is not the fatter upper and lower radiator hose) i started the engine and it reves high and then drops, ie, 2000 to 1200 rpm, and then it does it again, hi then low then hi then low again. i turned off engine, check the hose and lines around it, started engine and same thing.
Engine revs high and then low when starting?
You have a vacume (lean air mixture) somewhere.



Spray your connections (Hoses, Manafold Seals, Ect) of and to the intake (while engine is cold) with starting fluid.



Starting fluid is Nuclear compared to gas.



If you have a vacume leak it will suck it in to the (from the leaking connection) engine and rev the motor even higher then what it is, for a short period of burn off time.
Engine revs high and then low when starting?
vaccum leak get it to a shop tomorrow