if you know where your PCV is located, there's a rubber elbo that attaches to the top of the PCV at the back side, driver side of the motor. It may possibly have a worn hole or crack in it allowing an air leak. This will cause the engine to idle high, rough and probably cause the check engine light to illuminate.
I just did a head gasket on my 2001 Ford Taurus and did not notice that the rear EGR tube (the metal tube that comes off of the rear exhaust and recirculates the exhaust gases) had a gasket on the EGR valve located at the top of the EGR tube that connected to the intake manifold. The car would run until idle then go to 500 rpm and stall. Driving seemed to be ok as long as you did not have to stop. The car starts bucking and even in park goes crazy. Anyway, replaced the gasket between the egr valve and the intake manifold. Solved the problem. Note: 2 - 10mm bolts hold the egr valve to the intake assembly where the gasket goes. You may have to loosen the egr tube at the exhaust in order to get some room to disconnect these parts. You will need a 1 1/16 open end wrench and some rust buster.