Specs:
98 Civic SI (EX to you yanks)
Was automatic
Just finish B20B swap, converted to manual. Everything works, no CEL. Pulls hard with a B16 tranny.

My problem is my idle keeps hunting. From 2000rpm @ startup it goes a little squirly. It hunts from 700rpm to 1500rpm when I'm moving. As soon as I stop it goes to 1200rpm and levels out at around 1050rpm. Once in a blue moon it will idle smooth at 800rpm, where I want it.

I'm thinking IACV, but what can you check specifically to see if it's the problem? I'm no spring chicken when it comes to swaps and maintenance, but this ones got me beat.

 

Do you mean coasting with your foot off the pedal?

Have you cleaned the IACV?

Have you tried adjusting the idle speed?

Have you bled the cooling system?

Have you tested the ECT sensor and TPS?

 

Yes, when coasting foot off the pedal in neutral. It hunts. When I come to a stop, it levels out.

Cleaned it once. Made no differences. Will try to replace with a junkyard one. But there is no way of telling if they are good either.

I tried adjust idle speed. But gave up as it was having no effect.

Coolant system is bleed as per honda instructions. Coolant needle never goes higher then 1/3 the way, levels full with 200+kms on the swap.

 

Did you do the idle adjust exactly as specified in the service manual for your engine?

Have you tested the TPS and ECT sensor?

For 2-wire IACVs, you can measure the resistance across the two sensor terminals.

 

Nah I was more or less fiddling around with it. I was running low on time and patience.

TPS, no, but its never been touched. I'll triple check it tho.

ECT, no idea how to verify that one!

When my car idles low, you can hear the IACV humming....is that right or is it a sign of failure?

 

Also, sometimes it's clumbersome until 4000rpm then it seems to clear up. Very noticeable in mid throttle, kinda feels like vtec lol. In a terrible way tho....