Old goat

Guys what do the coolant lines that go thru the iacv do? Can they affect idle?

24TEN

iTrader: (2)

They route coolant like any other coolant line. I'd imagine if they were clogged or leaking badly enough that they wouldn't route the coolant properly to the IACV per your question.

94eg!

iTrader: (2)

If they were clogged, everything would be fine...they just wouldn't heat the IACV. The coolant is routed to them to prevent icing in the winter.... Now If the hoses were letting air into the system during cool-down, then you could have an idle problem. The most likely problem would just be leaking coolant under pressure (when hot).

Also check the seal on the lower half of the IACV that has the two nipples. Mine was leaking at this point cause the rubber seal was hard and cracked. Unfortunately you cannot get this rubber seal anywhere. I simply took the old hard broken pieces and coated them with Hondabond. Seemed to do the trick. No more leaks.

Here is a photo I found that's similar. Shows the seal and coolant chamber disassembled. This rubber seal was never sold separately for the CRX IACV (at least not my Si).

Old goat

Thanks for clearing that up for me.

~sp33~

Isn't the point of them that the flowing coolant heats the wax and adjusts your idle depending on coolant temperature? this aids idle up on cold start. If it's clogged your idle would be affected.

24TEN

iTrader: (2)

That's the way I understand it to work as well, but the OP asked about the lines not the IACV hence my response

94eg!

iTrader: (2)

No not in the IACV. You're thinking of the Fast-Idle-Thermo-Valve) which is a different device completely and mounted underneath the throttle body (and I'm not sure if any US CRXs came with). I know for sure the 89-91 Si has a Fast-Idle-Solenoid (ECU controlled on/off). Again a different device from the IACV.

Fast Idle Solenoid:



Fast Idle Thermo Valve

~sp33~

Yeah you're right. I just had a quick read of this too, really informative on Idle control and the IACV:

Honda IACV explained - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

TLDR:

IACV compensates for engine loading, FITV increases idle when the car is cold.

It doesn't explain why the IACV has coolant lines running to it though.

Old goat

Its in there sp33

The IAC valve is supplied heated water, via two small coolant hoses, to keep the valve from developing ice during cold operation. The IAC valve is not sensitive to the temperature increase from the heated water. The position of the IAC valve's plunger is totally dependent upon the amount of time the ground is on, which is controlled by the ECM.

nice write up