1988 Ford Bronco Ii Took Intake Plenum Throttle Body Off Clean Put New Gaskets

I have a Bronco II i took the intake Plenum and throttle body off to clean i put new gaskets on all the vacuum lines are on right when i crank it it will idle normal for a couple seconds then the check engine light comes on it does this every time i crank it the intake Plenum an manifold were cleaned off before i put the gasket on what else should i check