BMW: cold starting, air flow meter, oxygen sensor

Question
i have a 1990 325i with 225k, every morning when i start the engine, it will start right away but it idles erratically then after a minute it dies. I did replaced the air filter, fuel filter, spark plugs, rotor, distributor, thermostat and oxygen sensor all with new ones, i also tried to clean the idle control valve (t-shape) with wd40 as you said. I physically check all connectors and hoses but they're all look fine. I don't know what else to check , please just need a little help from you,, thank you very much, hope to hear from you soon..

Answer
Darren,
 Sounds good so far, except the WD40.  I only clean out the ICV with brake cleaner or starting fluid.  WD40 is a lubricant (like motor oil) and it will coat the inside of the ICV.  I doubt it will cause any problems right away, but I would try cleaning it out with starting fluid, contact cleaner, or brake cleaner.  These clean and evaporate immediately.
 You might check your Air Flow Meter (AFM) to make sure it's working correctly.  They do go bad after a while.  If you pop off the black cap on the top of the AFM you will see the internal workings of this piece.  There are some contacts that ride on a "track" on a circuit board, after a while these contacts wear through the board and it stops working correctly.  
 Good luck,
 Josh