ZCcivic91

I'm looking for suggestions on what to check out next to solve my Cold Idle hunting issues.

Car is a 96 Civic 4 door EX, swapped with a Completely stock B16A2, and a OBD1 Neptune ECU with a stock B16A2 map (at least thats what I was told the MAP was). Motor is out of Canadain 1999 SiR (Same as USDM 99 Si) so there is no FITV that I am aware of.

When starting the car cold, the idle hunts in a 500-1000 RPM range usually between 1500 and 2500 RPM. As soon as the car gets to operating temperature, the idle smooths out and is stable.

I changed the thermostat as the car seemed to also be taking a long time to get to temp, that fixed that issue, but after a few days the hunting came back.

I cleaned the IACV just to give it a shot, but my understanding is that the IACV only controls idle at operating temp. Didn't change anything.
.
I have Burped the cooling system. Ill be doing it again this weekend just to try again, but I believe I have gotten out all the air bubbles.

Other than the hunting at cold idle, the car seems to run great. No Codes on dash, and once its warm it never goes back to hunting. So from what I understand, the B16A2 cold idle for the most part is controlled by the ECU. Is there anything else mechanical I should check out before I have someone check the ECU?

Thanks for any informed suggestions.

ZCcivic91

Update, bled system again no change.

ill be seeing if I can borrow a known good IAVC to see if that solves the issues.

chrisc543

Does your throttle body have a fitv valve? Mine was fixed by utilizing this forum post.

https://honda-tech.com/forums/acura-...valve-1564019/

ZCcivic91

The complete swap is from a Canadian 99 EM1, there is no FITV on these motors that I am aware of.

Former User

Use your finger to cover the hole leading to the IACV inside the TB. Does the surging stop?

ZCcivic91

On my list to try when I have a few minuets, hopefully this afternoon. I'll update after.

Thanks

ZCcivic91

So I pulled off the intake.

Plugged the IACV hole and the car just nearly stalled out. I assume this is what its supposed to do when cold and the throttle is closed. I cleaned around the throttle body plate to make sure it was sealing properly, but it seems fine. I put the intake back on, Pulled the radio back to up reset the ECU (just to see, not even sure how that works on an OBD2 to OBD1 setup).

When I didn't have the IACV hole totally plugged, and jammed a paper towel in front of the plate to limit air flow a bit, it idled smooth although a bit low for a cold motor.

So now, not sure what to check into next. No codes on the dash. If I can find one, id still like to try a known good IACV. Ill have to try just adjusting the idle, and possibly the ECT sensor, but I cant imagine either of the helping in this case.

If anyone has any suggestions, feel free to toss them out!

Former User

Do the test when engine is fully warmed up. That's when the idle hunts, right?

ZCcivic91

Nope,idle only hunts when cold. As soon as car gets to operating temp, idle is steady.

James Bonds

Either iacv or tps but almost 100 % on the iacv. Clean it out real good with some paint thinner then reinstall. Try not to scrape it

ZCcivic91

cleaned it up once already with brake clean. I'm going to try it again with brake clean and then soak it in wd40 for a while.

Still trying ing to find a known good iacv from a 96+ vtec motor I can borrow from anyone I know. Once I have I'll give that a shot too and update.

Mdxwithspeed1

Was the problem ever fix with the IACV on your honda?

ZCcivic91

Super late answer to this, sorry.

It was never fixed with the OBD1 ECU I was using, which was a Neptune setup with what was supposed to be a stock B16A2 Map on it. It was definitely not a stock B16A2 MAP.

I have swapped over to using a P30 OBD2A Ecu from a 96/97 Del Sol Vtec, and it cleaned every problem up. Cold Idle Hunting Gone.

Mdxwithspeed1

So all you did was change the map sensor? I have the same problem with my 2001 Accord LX but after I cleaned it with brake clean the surging when away but I just get a high idle when engine cold and drops to normal when engine warms-up.
I swap the iacv about three times already and bleed the coolant more than one's with a coolant funnel and I get the same problem with the diagnosis I've done.
I know when the vehicle is in open loop the idle is a little high but the rpm's I'm getting with engine is cold is not normal.

Good job on your repair!