AztecEGhatch

I need some help sorting out the vacuum lines on my civic. Its a 94 CX hatch that I bought already swapped (b18a1 bottom end, b16a head and intake mani), whoever did the swap must have been retarted. I have already cleaned the IAC and FITV and it has a surging idle, even with the IAC unplugged. I tried covering one or both of the holes inside the throttle body which had no affect on how the engine idled (it still surged).

1. The vacuum line from the fuel pres. reg. was ran to the back of the intake manifold. Is this correct? (I have seen it ran to the air boost valve)

2. The air boost valve has a nipple not connected to any line (i saw a pic of another honda with the fpr attached to this), not the big one that goes to the intake mani, the smaller one. Where is this supposed to go?

3. The charcoal canister has a line coming off the top (I believe it is the one that regulates when it opens) that is not connected to anything, where should I connect this?

4. There is a line running from the charcoal canister to the throttle body (top) NEXT TO that line there is another hole that I can feel sucking in air (vacuum) when the engine is running, what is supposed to be connected to this?

I have searched a lot on this but it seems a lot of threads on vacuum lines go unsolved and i came across a lot of dead links. please dont just put up a vacuum diagram because i know how to use google images and this does not help me, also I seem to not have any firewall-mounted solenoid valves or MAP??

Hopefully you guys can help me out on this because it is very confusing and frustrating

HondaPartsHero

See if this helps or post a pic of the manifold. There are at least 3 B16A manifolds and throttle bodies so it'll help determine it better.

sfar785

that hole that you feel air sucking into, i just capped mine off. When it's not capped mine idled really high, after capped it idled back down to 800/1000rpm's.

AztecEGhatch

that diagram sort of helps, at least with the canister. Did civics come EVAP solenoids or is that something i need to get (off of a teg or something) ?

This is my intake mani:





do you know the function of it or what it is called? I plugged mine with my finger and it didnt do anything probably because i have a crazy vacuum leak

sfar785

make sure you're not getting a leak from the intake manifold gasket...although i'm not sure what the one nipple does but i will look it up later

AztecEGhatch

Ill check the manifold gasket for leaks in a bit, im very upset with my civic now though and its in time-out in the garage

sfar785

if all you have are vacuum leaks consider yourself lucky...i just swapped in another b18b1 into my EG coupe and ran into a bunch of problems, 99% of them were user error but everything seems fine now...but i wish a vacuum leak was all that plagued my Honda for a few weeks

AztecEGhatch

yeah its more frustration towards the previous owner. He made it sound like hes all about clean cars/swaps and doing everything properly and now the more i learn about hondas the more i realize what was half-assed or skipped over. Also he lied about a few things and now im starting to think he lied about the ARP head studs and ACT clutch...

anyway, thanks for the help so far and keep it coming. I want to figure this small mess out and get my civic running properly with no shortcuts or rigging

AztecEGhatch

any more help on this? whats your FRP vacuum line hooked up to?

sfar785

Post a pic and highlight the hose in question, I can't do much seeing as how my computer decided to die on me and I'm stuck on my phone for the time being.

AztecEGhatch

Alright I took some pictures, lets see if you guys can help me out with whats missing and what should go where.

AztecEGhatch

There has to be some one else running a boost control solenoid that can tell me where the vac. line is supposed to run.. come on, any help appreciated.. even just a pic of your intake manifold

DCRB

EDIT: I posted wrong info before.

o/p part of your problem appears to be that you have an obd-0 intake manifold with a newer obd1/2 throttle body, and it's missing the idle adjustment screw.

the fpr line is fine, as is the brake booster line. the vacuum boost control solenoid thing on the stock b16 has a small line running from the intake tubing to that nipple, looking on line it looks like people just cap it off. newer obd0 intake manifolds don't even have that on there from factory.

the purple cap that's plugged off is supposed to go to your pcv valve which you apparently don't have hooked up.

i know this diagram is for a b18a1 but it has the same manifold:




o/p i'd personally source a newer b16/itr intake manifold to make work easier. alternatively you can remove the boost solenoid, and use proper size set screws with teflon tape, and remove the vacuum bung, tap that hole, and insert another set screw.

found the info here:
https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/b18a1-vacuum-diagram-questions-2638675/

morbius18

I think that I'd invest in an obd1 aftermarket or p30 manifold before retrofitting that one. Seems like half assing the previous owner did is all too common.

AztecEGhatch

Okay, so it looks like I should hook that line from the canister to a vacuum source to get that working. I believe the one that is capped off should be fine because theres a catch can and the prev. owner removed the PCV. I will have to get a set screw for the throttle body. Only thing I was confused on was how you described removing the boost solenoid, not sure where the set screws go

very helpful, thanks!

DCRB

.... you need to re install the pcv valve.

basically if you unbolt the boost valve there will be 2-3 bolt holes in the intake manifold. idk if those holes go through, if they do you'll have to seal them up, using the bolts that holds the boost solenoid or using some set screws. the main one i was telling you to remove though is the large vacuum nipple that comes from above the IACV. hit it with a hammer till it twists out, then tap the hole that's left (the nipples are just pressed in) and screw in a set screw.

the vacuum line from the charcoal canister that isn't hooked up on your motor is supposed to first go to another control solenoid that is controlled by the ecu, then from there a vacuum line goes from the solenoid to the intake manifold. the charcoal canister is not needed for emissions (unless you live in cali) and you can simply ditch it, cap off the line on the tb and run a piece of hose from the fire wall vent to the ground.

AztecEGhatch

Okay I ditched the canister and made some progress.

After cleaning the FITV and IAC again. The engine was idling a little lower (around 1500-2000) and still surging/inconsistent. When I unplugged the IAC and covered the bottom hole on the inside of the throttle body, the engine would idle almost perfect (around 800, dont have the air adjuster on the TB yet)

So what Im asking is does this mean my IAC is faulty (does the hole I covered (bottom) go to IAC or FITV)

AztecEGhatch

I read that if you cover the bottom hole and the idle goes down, the FITV is faulty. My idle goes down when I cover that but only when my IAC is unplugged as well, it doesnt make a difference if the IAC is plugged in.

I also read that if you cover both holes and the engine dies which means the IAC is faulty, I covered both holes and the engine died.

I am pretty sure my IAC is faulty, I have cleaned it twice and the engine always idles lower when its unplugged. Could my FITV be faulty as well?