Hey guys 👋.



B18B1 out of a manual 1998 Integra swapped into a 1999 Civic using the D series harness with countless modifications using a OBD2B to OBD2A jumper into the Integra ECU which if i’m not mistaken is a P75. Only code in the system is for secondary 02 (it is not there).



I am having a weird idle issue. In the last few weeks I have done a lot of diagnosing but still haven’t found the root cause. Originally replaced the IACV as the vehicle was not able to idle on its own only until it reached operating temp. In order to get the car running you have to apply throttle to start then hold the throttle at about 1k RPMs until vehicle reaches temp. Once it reaches temp it will idle but very low around 300-400 RPMs.



From time to time the vehicle would have a power cut off then back on while driving. Occasionally (not often) the vehicle would completely shut off and would not turn back on. Only after letting it sit for a few mins it would start again.



After the IACV was replaced I was getting a code for the wiring. I re-did the wiring to the IACV cleared the codes and started the vehicle up again.



The vehicle began to do an automatic relearn (still unconfirmed if it’s attempting to learn or just idling high) the vehicle was idle surging from 1000-3000 over and over. I was reading online to let the vehicle get to temp, let the fans cycle on twice (once this sequence is completed you should be able to shut the vehicle off then turn back on again and the idle would be better. As you drive it would also adapt and get better overtime) **TO MY KNOWLEDGE**



I let that operation complete its steps. When I went to turn the vehicle on it did not start.



Turns out the reason it was cutting out was due to a bad distrib coil. Tried a known good one and the vehicle started up again. Also replaced the 15A Ignition coil fuse in the cab (it was blown).



Once I replaced the coil and the fuse the vehicle attempted to do “the IACV relearn”. I again let the steps complete and when i went to turn the car on it was idle surging again as if it didn’t relearn.



At this point after some more research I cleaned out my PCV joint and checked for vacuum leaks. Found a leak from my throttle-body gasket. Replaced the gasket and tested for leaks again using a smoke tester - no further leaks.



I started the car up and it began to idle at 1100-1200 (cold) which was the first time it’s done this.



I took it for a short drive and the vehicle got up to temp. Once it reached temp it shut off. After it shut off I had to apply throttle to start it, once started I had to constantly keep a throttle on otherwise the car would shut off. After some more driving the car would stay on without throttle but the idle would jump from 1000-1500 constantly as if I was just reviving the car over and over.



This is where i concluded my diagnostic. Also I fully bled the cooling system before any of this (took like 2 hours).



Please let me know if any of you require more info. Any help or guidance is appreciated, thanks guys.

 

UPDATE

Hey guys, so I had my original IACV (OEM) ultra sonic cleaned. Lots of goop came out of the valve area. I put a lead to the unit to make sure the valve operates and it did. Swapped it back on my intake and now the vehicle idles correctly. Used a scan tool to set the idle within parameters around 750 ish. Turns out the aftermarket IACV I bought was indeed faulty.

On a side note was running live data during idle and my short term fuel trim was -17 running rich on idle it seems. Anyone have any experience with overfueling?

 

What fuel pump do you have in the tank ?

 

I currently have the OEM one car is sitting around 370KMS no idea if it’s ever been done. I actually have a Walbro 440 to go in just haven’t had the time recently.

 

Big fuel pumps typically increase the system fuel pressure due to the increased pumping volume through stock sized fuel lines... thus, causing a slightly rich condition throughout the fuel maps. In this case, it would not be uncommon to see fuel trims like yours.