I have a problem with my car, every-time I start it up the engine will start to rev when below 1000 RPM's. The weird thing about it is the car will stop revving, even when I go above 1000 RPM's the car will stop until it reaches below 1000 RPM's. The car is a 1995 Cavalier Z24 2.3L. We had just taken the engine out and did the following:
-Head gasket..
-Water pump.
-Oil pump.
-Oxygen sensor (bosh)
-Timing chain and gears.
-Timing belt and pulley seals.
-Gasket for the timing gear plate.
-Sparkplugs (Ac delco)
-Vacuum line.

A few things I did was:
-Clean out the oil pan with varsol and cleaned it all up.
-Cleaned up the header.
-Sprayed out the throttle out with throttle-body cleaner.