1993 se wont idle

my fiance has a 1993 grand am se with a 3300 v6 and 3 speed auto tranny. the car has about 87k miles on it, the engine has about 2k miles. we bought it with a blown engine, there were 2 BIG holes in the block...and it still ran! it has new plugs, wires, air filter, fuel filter, the works. the problem is that when we start the car the idle goes up to 1500 rpm's then drops to about 500 rpm's, it will jump back up to about 1500-2000 rpm's, it will drop to about 500 and then stall out. the first thing i thought of is the idle air controle valve. i bough a new one, installed it and reconected the battery. it still does it. i was gonna take it to autozone to get it scanned but since there hasnt been a CEL since it reconnected the battery that wont tell me any thing. the car is not driveable at the time so any help that any one can give me is greatly apreciated. if you need to talk to me im on AIM- daewoomofo and MSN Messanger- [email protected]. thank you for any help

Welcome to AF!!

I would check three items, first check for a vacuum leak. Even though this is a new engine this is a possibility. Second, check the throttle position sensor to make sure it is working properly. Finally, check the MAP sensor. It may be sending incorrect readings to the ECM and causing the idle issue.

Finally, if everything checks out you may have to replace the ECM to correct the issue. Sometimes they will interpret information incorrectly and cause radical idle changes. These are the only things I can think of off the top of my head that would cause this. Of course other members may have additional suggestions.

could be a bad intake manifold gasket, thus causing a vacume leak, causing the high idle. while its running spray some carb cleaner around the outside of the intake, if your idle changes drastically you found your problem.

start checking vacume lines, then intake gasket, then get into trying parts like the thoratle position sensor, & map sensor.