my 95 chevy astro van is acting funny. just changed the alternator and now as the van is idling it sometimes fluctuates as if the gas is being pushed slightly and then let off. it does this as im driving also, though it is less noticeable but you can still hear the engine sound like it is rev-ing alil bit in a rythemic pattern. i spliced the A and B pin to pull the service engine soon light code. i recieved two codes code 12 and code 23. does any1 have any recommendations as to where i should go from there? also while the airbox was off i had never noticed this before but it sounded as if it was whistling kinda like a high pitched whooshing whistling sound periodically.

Thank you for any help
Aaron

 

12 means your ecm is up and running. I assume you have fuel injection then code 23 would mean IAT low temp indication, the code will set if the air temperature sensor, connections or wires are open for 3 seconds