HI all.
Im new here and I just aquired a 2000 civic Hx i wanna to figure out what this idle bounce is. Its starting to get annoying.
It only happens on cold starts and only in gear. the idle bounces from 300-1200 rpm when at a stop in gear on a red light.
the previous owner gave it it a full tune up before i bought it.
im assuming its the IACV because it happend to my crx awhile back but not 100% sure. no check engine light nothing everything seems normal except the idle bounce when it cold. idle doesnt bounce if the car is in park only when in gear.

 

Clean the IACV, the FITV, the EGR and all of the EGR runners and see if that helps. You might also check your coolant level, I think I read somewhere that the FITV will read wrong if you're low on coolant.

 

coolant is full i checked that already. take apart the IACV this weekend to clean it and see whats up.

 

That is definitely a vacuum leak.