My girlfriends car,

when she's say, waiting at a light or stopped in traffic, the idle will be normal, then all of a sudden it dips way down almost stalling the vehicle, then climbs, and drops until she gives it a bit of gas.

Any Idea what the problem here may be?

 

not 100% sure about this. but i'm having the same problem right now with my civic..in neutral it rev's up and then down..not to the point of almost stall though..but from what i've collected through h-t + sohchonda.com i THINK its one of two things..either tp sensor or eacv.

 

i'm thinkin something with vacuum pressure/ or lack of

 

How do I go about checking those problems?