I have a 1993 Honda Civic Hatchback DX. I just recently swapped out the d15 and swapped in a d16y7 from a 96 DX. When i had the d15 in the car my idle was doing the humpty dance (idle jumps from 1.5k to 2.5k). i switched the d16 over to obd1 from obd2. So on the d16 i added the following from the d15. intake manifold, dizzy, injectors, alternator, ecu, and wiring harness. The d16 is now in and this motor is also doing the humpty dance. the only thing that makes it idle normal is when i unplug the iac valve. there is enough coolant to the manifold, i cleaned the iac valve, there are NO vaccume leaks. So does this mean i have a bad iac valve and should order a new one? PLEASE HELP!!!! thanks in advance.

 

you are positive you have no vaccum leaks?

 

yes

 

did you clean the iac passage also? if the passage is clean and there is no vaccum leaks, then i would say replace iac