iac problem

[89 hatch]

I have a dohc zc that revs up and down at idle. Ive changed the iac and the ecu, is there any other problem that can cause that. also when I unplug the iac it idles fine but wont go over 3000 rpm thanks

 

[charleskwinter]

clean, maybe replace, check for vacuum leaks (you can search these topics too)

 

[8ballsin]

look at the ecu what is the fault code if it is 3 or 5 it is your map sensor the reason i know this is because i had the same problem but fixed it 4 hours ago

 

[INJEN78]

vaccum leaks,map sensor(as 8ball said) tps might do that..but try resetting the ecu..unhook the neg. battery cable for 5 minutes

 

[m90polk]

I would definetly go with a bad vacuum line because that is what usually makes it surge at an idle, but also check the electronic plug to the IAC for the right voltage and for no shorts to ground or anything like that