Ok, ever since I put my B18B into my hatch I have had really erratic idle surges. It fluctuates between 250 RPMs and 1200 RPMs. I've tried new IACV's, I've cleaned the hell out of the front and back of the throttle plate, and I've cleaned out both IAC passages in the TB. I am totally confused as to what it may be.....the only thing I can think of is that it may be a vaccum leak since its spitting out about 200 PPM HC's but it cleans up once I bring the RPM's about 1200. Any ideas?

 

I had the same problem and a fellow honda tech member told me to do this and it fixed it.
Wait until car reaches normal operating temperature, disconnect iacv, raise the idle . You will get a cel, pull hazard fuse and reinstall.
I bet that will fix it.

 

you can also try bleeding your cooling system... any air pockets will cause an rpm surge when the engine is hot.

 

The coolant system sounds like a good place to start. Think a full fluid flush would help? I haven't flushed my whole system in over a year.

 

If you just installed the B18 and it started doing this then a likely candidate is the cooling system. It has happened to me a couple times at work after a timing belt job or swaps... any job where you have to empty the cooling system and refill it. Scared the **** out of me the first time it happened, i thought i screwed something up.

you can either burp it or just open the bleeder and keep filling it till all the bubbles are gone.... however, if the idle is hunting and not surging (hunting is like a small idle surge, not a large one like you described) then i would check the map and the iac.

 

SOmetimes it hunts, sometimes it surges.....hell I think I'll just start with a coolant system flush....never hurts to do general maintenence anyway. I'll repost if that doens't solve the problem.


It only has the problem at idle, and its only really bad when you start the car.....for some reason after the initial start if you go into reverse it likes to die when you put it into neutral. ******* swapped cars.