Hey everyone, I'm currently having some idling problems with my b16.
I have a 1998 civic DX hatch with a full b16a2 (em1) swap. Its paired with a chipped p06 and vtec does engage.
Currently, my issues are when i start my car cold, it has an extremely high idle, around 2.5k-3k rpm. It slowly decreases as the temps rise. Then after reaching operating temp, it idles with a slight bounce, 1k-1.5k rpm. Also, when driving, it the rpms randomly drop below 400 and it almost dies, on rare instances (especially on hills) it would shut off completely.

It does this constantly.
Here are things that I have already done/ diagnosed:
1. Searched for obviously vacuum leaks, found a crack in my throttle body gasket, replaced it and made the idle better (it was way worse before, it would jump from 800-2500 rpm)
2. Made sure every hose has a start and end point and/ or was plugged.
3. Cleaned iacv to no avail, ended up replacing It, again, helped the idle, but didn't fix it completely.
4. Some misc stuff was replaced the TPS and readjusted timing.

At this point I am lost and have no idea where to look next. A few buddies pointed out that my ecu could be the issue, does this hold any truth? Im aware the p06 is a sohc ecu and probably isnt the best ecu to run with the swap. Any ideas would be amazing and i appreciate it in advance. Thank you.

 

I’m guessing you already troubleshoot the IACV that is mounted on the intake manifold, but have you checked the Fast Idle Control Valve?
Fast Idle Control Valve is mounted directly on the throttle body. This will affect idle when the spring mechanism gets stuck inside.
I’m guessing since this is an old engine, and probably never had the Fast Idle Valve serviced, if so.. this is highly likely the issue.

Check out the video below that I found on youtube.

Also, other things to check are…
Do you still have EVAP/Charcoal canister?
Are you using PCV valve? Or External Breather?

If you are using EVAP and PCV, you can completely unplug them and block off the vacuum lines going into them.
Chipped ECU most would have EVAP disabled in the settings anyway, so no need to have them even plugged in.

 

Also, wanted to point out one more thing here.
There is absolutely nothing wrong with running a P06 as long as it’s chipped and you have B16A2 compatible basemap running on it.
any OBD1 ecu can be converted into a P28 counterpart during the chipping process.
What’s more important here is what basemap you are running with the chipped ECU.

 

Also, other things to check are…
Do you still have EVAP/Charcoal canister?
Are you using PCV valve? Or External Breather?

Okay so, I running an aftermarket throttle body that does not have a Fitv on the bottom. I should also mention I bought the car with the swap and knowing it had the problem.
Anyway, I'd have to double check in the morning, but I do have a evap/ charcoal canister delete, would this affect idle? And I'd have to look at the PCV valve again. I'll update you on everything I know.
None the less, thank you for your response.

 

If you removed EVAP, you shouldn’t have problem with the idle.
I don’t know which manifold you have but, there are some intake manifold that has vacuum nipple/port on the bottom side as well.
Make sure those are plugged up and not introducing more air.

At this point, it seems more like a vacuum leak since you don’t have Fast Idle Valve, and also deleted the EVAP.