Hey guys, I just recently purchased a ride with the b18a swap done to it and the guy who did it had to make some custom motor mounts all around. Now when I say this, it went into a 1982 Honda Prelude........so you get what I'm saying. lol. The car has had the classic idle issues and first thing I did was clean/adjust the FITV and IACV on the manifold. I reset the idle under factory specs and its now idling between 900-1500. I've looked it all over and can't seem to locate any vacuum leaks, all the hoses have been replaced and are connected to their correct spots (unless I'm overlooking something). But when I was under the car admiring the swap, I noticed the custom mount the guy before me made was using the rear mount location on the transmission and was digging into the black box. There's a huge crack going form the top of it down halfway and I'm not sure if it's pushing it outward from the huge hole in the block that it connects to on the bottom. I haven't been able to run the car and check to see if it's leaking here but could this cause erratic idling issues if cracked or open like I'm describing?

 

First off, what kind of idle issues are you having? Do you have a low, high, surging idle? I assume your talking about a surging idle. And are you talking about the catch can that the PCV plugs into? if so, I would say yes, a vacuum leak there could cause an idle issue. But more likely its related to the IACV. Even if the IACV is clean, that doesn't mean its working properly. I had a problem with my idle before and found that wire harness going to the IACV was rubbing on a bracket and cause a it to short out. Mose surging idle issues are related to the IACV.

 

It's a surging idle when the car warms up. I was tempted to see if the IACV is bad but then again the crack in the PCV system is what I'm asking.

 

Check for leaks if none IACV is bad replace it

 

If its a surging idle, then check the IACV first. Vacuum leak would more likely just give you a high idle. First inspect the wires going to the IACV. Then check the volts going to the IACV. See if its getting a good signal from the ECU. Are you getting any CEL codes? A p0505 and p1508 would be problems with IACV. You should be getting battery V on terminal #2 of the IACV connector with the key ON. Try disconnecting the IACV while the engine is on. The idle should drop or stall. If it doesn't, its probably a bad IACV

 

try adjusting the idle as per procedure. that is, disconnect iacv, adjust to 500rpm, reconnect iacv. idle should sit at 750 roughly. clear code and allow idle relearn. an incorrectly set idle can cause confusion for the ecm and it's command to the iacv.

and actually, a vac leak shouldn't cause any idle issues. that's what the iacv is for. to regulate idle. as soon as unmetered air is allowed in, that iacv will close a certain number of "counts", keeping idle at its desired 750rpm. it's really a cool little actuator.
have you tried cleaning the actual port for the iacv? pull the intake boot off, start the car and let it warm up. using throttlebody cleaner with the nozzle straw, spray liberally into the top port (bottom is fitv port). snap the throttle a few times while doing this. repeat a few times. because of the restriction in the port, it inherits itself to clogging and can cause these issues.
while you're in there, put your finger over the fitv port. if idle smooths out, problem is fitv related.

another possibility is a bad fuel pressure reg, or fuel system issue. try installing a fuel pressure gauge. see where you're at there. we can run through some tests using just the gauge. a little more in depth than simply testing fuel pressure

 

Sounds like he knows what he's saying so ill take good advice...

 

Actually this is superb advise guys and I thank you greatly. I was able to clean the IACV a few weeks ago alongside adjusting the FITV but it seemed to have gotten worse. I did spray some carb cleaner around the gaskets/orings and found no leaks so it seems good in that department. I'll have to try the finger trick on blocking the ports to see if there is any change as well as disconnecting it. Maybe the IACV just magically crapped out but we'll see. Hoping tomorrow I'll be able to put it on ramps and give it a check. I'll post back.

 

Did you check all the wiring to the IACV? You need to test the voltage at the IACV and the ECU. Are you getting any CEL Codes?

 

These guys are giving good advise on the electrical stuff, but if you can see a crack in the black box you should repair or replace it. A vacuum leak will always cause some sort of problem. Start with what you know is wrong, then if the issue persists continue with diagnosis. Good luck!

 

Exactly and that was the first thing I went after when we finally got a good look at it. Apparently I was seeing things I guess last time and the breather box isn't even cracked but the rubber covering on the outside is. It's slightly ripped and behind it is the metal box. We made sure no vapors or leaks were taking place around it so I guess we're good.

I moved on to any other possible leads and we checked the IACV & FITV again. The FITV was in screwed in place and the seals were good. The IACV was good, clean and the seal was good. So we tried the finger trick on the TB and the FITV is closing at warmup so it's healthy, but the IACV will kill the engine if you plug up it's hole. Tried it twice and it dies instantly. Not sure if this is a sign it's bad or it's normal since I'm reading conflicting differences online.

We decided to reset the idle by unplugging the IACV and adjusting, turning the car off, plug it back in and restart the car and guess what.....NO more idle hunting. Guess the last thing on our list was indeed the idle adjustment which was throwing the IACV off. Glad we put a list together and thanks to your guys help. It's not a perfect idle as it slightly moves just a hair up and down (like between 100 rpms) but is tons better than going about 500-600 rpms in roaming.

 

glad its all sorted. and dont worry, its perfectly normal to stall the engine when covering the iac port. that port is the only means of air for the engine at idle. covering it starves it. if anything, that just proves you don't have any vac leaks, since it would have stayed running with it covered

 

Guess this is true, never thought of that! Thanks for the help guys!