Alright, I have a friend who has a 93 Civic Cx with a H22 swap. The swap was done professionally but we can't figure out why it's idealing funny. It rev up to a 1,500 and then drop to 1,300 and then rev back upto 1,500. It's going up and down like it's cool any advice would be appreciated.

 

does it only do this when its idling? if so its honda's way of 'priming' the motor to the correct RPMs

 

Sounds like it could be a vaccum leak or a faulty IACV.

 

as soon as i did my swap i had the same problem when we started it up...changed the pcv valve and it was fine...also just spray some water lightly on the hoses and check for any signs of water bubbling or anything.


Good Luck!