Ok so I have been searching on this forum and have tried a couple of things mentioned on here too!

My issue is the Idle surging on the B20 which is installed in a 2000 civic EX(SOHC Vtec)

1-So far i have Opened up the Fast idle Valve and worked it all the way down, i ran the engine and placed my finger on the lower hole inside the TB and it had a small amount of suction, until the engine was warmed up and radiator fan turned on, i had no suction on that same opening inside the TB! so this works fine now.
2- I replaced the IACV with a BRAND NEW OEM one and for about 50km it was fine then i noticed when i come to a stop the idle drops to the normal 750rpm range and then jumps back up to 1500 and then slowly back down to normal idle and remains there.. the needle doesn't bounce up and down like a bad IAC would do.
3. So i thought maybe the TPS is out of range and cant find the closed position when the car is coming to a rest, so i check with a Voltmeter and followed the steps on the Haynes manual and it is within spec. i also played around with the idle screw and closed position screw at the bottom of the throttle cable plate.
4. I replaced the ECT sensor and bleed the coolant system also.
5. I am currently running a 2001 CRV 5speed ECU and have NO CEL lights, car runs fine just the idle at stop is acting up.. Now I put back my OBD1 P28 B20 Chipped ECU and the car runs perfect!!!! but cant do smog test with that ECU. so Im F**K'd

Is there a wire that i should maybe switch around on the harness? because the OBD1 ecu does Not give me that idle surge when i come to a stop, The idle just comes down to 750 +/- 50rpm and stays there.

This is getting frustrating i have tried many things, but the engine still wont run right. im at the point of buying a B20Z same year as the ECU so i dont have to jump anything and everything is pretty much plug and play.

 

you didnt mention if you bled the cooling system

 

Ya i did that in Step 4
replaced ECT and bleed the system

I did Also vacuum leak test before i replaced any parts, because that would have been cheapest fix! found nothing no Leaks.

 

If you use your finger to cover the hole in the TB leading to the IACV, does the idle speed drop and surging stop?

 

only when i beat the crap out of the car and force a CEL light then yes if i plugged that hole it idles down. This is a NEW IACV installed though. and it Runs Fine with a P28 ECU b20 chip And i Get a code after 30km with OBD2B "PHK" ECU for P0505

My main concern is the idle bump after letting off the gas completely at no load
ill take a video of it with my phone when i get a chance. this is what i think causes the IACV to start acting up after driving for a while, so im wondering if the PHK ecu has diff pin location for IAC/MAP/TPS and maybe thats why its messed up.

 

Are you using a 2 wire, or 3 wire IACV?

 

2wire IAC

 

OK... so unfortunately after spending all this time and money and still cant figure out the wiring issues between ECU's i tried doing etest to get at least a conditional pass, and was refused, also i tried to get a tail pipe test and was denied, my car is now flagged and is unable to be put on the road, unless I return everything back to Stock and now have to go to a Gov Emission testing facility with proof.. this is such a horrible law they have implemented, if my vehicle was a 99 or older i would have been allowed a reg tail pipe test and pass! now i have a giant paper weight on my driveway until i can decide what to do.

 

If you live in a state that requires this why are you running it with a p28?

Edit: What harness are you using? What injectors? B20b engines don't have a FITV? Has the immobilizer chip been removed from the CRV ecu? Is the ecu for 2wd or 4wd?

 

using a 00' SOHC vtec harness, LS injectors with fuel rail, LS ITM withTB & FITV , and it does not have an immobilzer on the CRV 2wd 5speed ECU.