blazzer

b16a gen 2 engine (fully stock)
P30 ecu
hunting idle & high idle only when warm
Cold idle is fine

So i have two (2) IACV's (one installed one not) one reads 10 ohms the other read 11 ohms.

from what i understand these are both within spec.

when installed and running on the car blocking off the top port in the TB for the IACV the idle calms down, i dont fully understand what this means, is the IACV bad or good?

should the idle when this port is blocked off stall the engine out? or should it calm the idle and keep the engine alive if the Iacv is Good?

I have done these and ruled them out as a problem:
There is NO CEL!
cleaned fitv (reset/screwed piston back to seat)
cleaned eacv
checked vacuum lines
checked pcv
cleaned throttle body & replaced gaskets
coolant flush
checked ign. timing.
tps .48 closed, 4.53 WOT
coolant temp sensor (286 ohm)

Former User

Does the CEL work?
What happens to the idle speed when the IACV is unplugged?
Have you tried adjusting the idle speed as per instructions in the service manual?
Does the engine warm up quickly (~5 minutes) from a cold start as determined by watching the cluster temp gauge?
Did you Ohm test the ECT sensor when the engine was fully warmed up?
Have you thoroughly bled the cooling system?

blazzer

Yep i have confirmed the cel works.

when the IACV is unplugged the Idle drops down and calms down with no hunting to about 600 rpm and stays steady.

Yep i have tried adjusting idle speed as per manual instructions. currently after properly re-adjusting idle the lowest idle it will go is 1000 Rpm

sitting at idle, engine takes about 10-15 mins to idle at an atmospheric temp of about 5c ( think that is 41F?) watching the needle rise, maybe about 20 mins at most for the first rad fan activation.

yes i did. i took the car out for a test drive, engine was fully warm, once i got back i let the rad fan kick in twice, and then measured the ECT ( took me a min to get he plug off and had to change mulitmeter batteries)
The ECT reading was 286 Ohm, i re tested the ECT today after 2 rad fan activations and it was reading 271 Ohm.

Yes cooling system has been thoroughly bled.

Former User

What's the idle adjust procedure for the P30? Is it like 5th generation Civics - warm up engine, unplug IACV, adjust base idle speed to 420 rpm, turn off engine, and reset ECU?

How did you bleed the cooling system?

Is the throttle cable adjusted to have some slack?

Do you know whether somebody tampered with the throttle stop screw?

blazzer

Idle procedure is exactly like you said. Although i will mention with that procedure, lowest idle i can achieve right now is 600 +/- 50 rpm.

i cannot specifically hit 420 +/- 50rpm. Idle screw is set all the way in, if i back it out it raises the idle.

bleeding the cooling system i used the bleeder valve by the thermostat, bled while topping up until there was a steady stream of coolant with no bubbles.
upon that, Started engine with the rad cap off.

coolant burped a couple times, topped off, let the engine run fora while to make sure air pockets had cleared.

made sure the resivor was topped properly as well.

Made sure that when bleeding the heater core valve was open(set to hot) and when the engine ran to bleed from the rad. that it got to temp as well.

Former User

This^ is clearly an issue.

Also, has the routing of any coolant hoses been modified?

blazzer

Yep it is, I am not 100% sure what to do about it right now. Wanted to at least figure out the hunting issue then tackle this problem. I am assuming they are related some how.. maybe a faulty TB?



Nope, no modification that i can see and have inspected on myself.

Former User

These^ two issues are almost surely related.

At this point, I think you should focus here:

blazzer

Hmmm what would be a good place to explore for this? I have run out of idea's on how to get the idle adjustment lower.. and fix the hunting idle?

Yep there is slack. when i first got the car, there was no slack at all. I removed the cable and followed the manual for proper install and adjustment.

As far as i can tell the stop screw has not been tampered with. It has the factory Markings on it still for both the stop screw and nut on the throttle lever.

I can go take some pics if need be.

Former User

Has this car/engine set up ever idled correctly since you owned it?

blazzer

No not to spec.

When i first got the car the engine was running off of a p72 ecu.

The first thing i did was convert from the obd2a to obd1 and install a p30 ecu.

since that it idled better with no hunting. about a month after that it had started idleing really bad cold and hot and hunting dramatically.

Cold idle would hunt but only slightly, around 2000-2500 rpm

warm idle would idle around 1800 and hunt from 1800-3500 rpm.

I cleaned the FITV and re-set the plunger/piston and that seemed to fix the Cold idle.

I Took the TB off and cleaned it with TB cleaner, replaced the Gaskets Cleaned the IACV.

This seemed to some what fix the drama of the idle and hunting but was not a cure.

currently warm idle is at best 900-1000 rpm and hunts between 1000-1700ish.

Re-installation was followed with a manual and all torqued to spec.

Former User

Is air possibly leaking past or through the idle adjust screw?

blazzer

I do not believe so, but i have not confirmed this or tested at all.

The screw is fully set in at the moment.
I cannot hear hissing from it if it was leaking substantially.

*edit*
I will Test this to make sure and report back.

blazzer

I still need to check the idle screw for a vacuum leak but i had some time so i did a map test as i never got around to that and well... did it now.

So did a map test.
(grounded to map plug so D12)
from D3 = 4.78V (red/green)

From D4 = 4.96V (yellow/red)


Ohm from map:

D3 Pin on map 10.09 Ohm (red/green)

D4 pin on map 3.47 Ohm (yellow/red)

Former User

You could try covering the hole for the screw with your finger to see whether the idle surging stops.

However, I think a previous owner may have tampered with the throttle stop screw.

blazzer

hmmm. ill take some picks of and post them up this afternoon or this evening and get you opinion on the idle stop screw and post the idle adjustment screw results later on as well.

I forgot to mention. when i was doing the MAP test yesterday night, when i had the key to IGN.on but the engine not running, i had noticed the IACV was making a decently loud whining sound.
I have never heard this before and i cannot see this being normal?

blazzer

Ok so, got the engine to temp. plugged the idle adjustment screw, no change in idle hunting.

also got some pics of the TB stop nut.

blazzer

Ok this is the weirdest thing. i went to move the map sensor and vacuum line. It was originally zip tied to the fuel line and to be held somewhere. messy so i cleaned it up.
upon doing this the idle has dramatically calmed down..... i am really lost as to what i have done or what has happened to cause this.

the only thing it does not is idles a little high. like 900-1000 rpm and when i hit the gas, as the rpm's come down, it jumps up about 100 rpm ish then goes back to idle.

sounds confusing but check out the video.

im serious lost though. i checked the vacuum line on the map so many times and the plug in for the map as well..... 0_o

And i would like to note that when trying to set the base idle by disconnecting the iacv, it is still idling around 600 rpm, not 420.
right confused.

Former User

There was a vacuum leak from the MAP sensor hose. I'm surprised that it's still not possible to drop the base idle speed to 420 rpm. Perhaps there's still some leakage from the MAP sensor or its hose. Post pictures.

blazzer

ill have map pictures up 2morrow morning. been a busy week.

I would like to update though there is still the hunting problem. Sort of a new symptom though, The hunting randomly show's up and sometimes does not show up but when it does it is fairly obvious. I wonder if the map sensor it self needs to be replaced? even after running the map tests and they seem to be in spec?

I checked all map wires for breakage/corrosion/ proper voltage and continuity

idle is 900-1000 rpm and trying to set the idle via disconnecting the Iacv and adjusting the idle screw is very UN-succsesful.
According to the manual, rpm with the iacv disconnected should be in spec at around 420 rpm +/- 50 rpm and the lowest it will go is 750.

Deff. something still going on here and the more i do the less it can be so i have no idea.

I took the VC off to check for maybe some kind of visual damage but i could not see anything obvious or subtle.

blazzer

so small update. got video.

ill explain here in case the video makes no sense.

when the engine is surging/hunting. blocking the iacv fixes the problem.
when the engine is surging/hunting pushing the throttle body pulley forward ( closed) the idle calms down and seem to set at a better idle.
pressure off the pulley from my hand the idle climbs maybe 100 rpm but does not hunt.
when throttle is applied, hunting begins again. repeat with closing pulley problems seems to go away.

is this an indication of a bad throttle body? bad butterfly vavle? poor TB pulley spring tension? or a vacuum leak directly from the tb?



also, when trying to set base idle;
disconnecting Iacv plug, hunting stop, engine idles around 700 rpm. Idle screw is fully set and cannot drop the idle lower.

why is this?

Hunting/surging:

Base idle:


also as requested Ron here are pics of the map sensor and how it is setup:



if there was a leak from the map, would it not give it a weird reading and cause the car to stall rather then have a fluctuating idle speed and overall high rpm due to the somewhat atmospheric reading?

blazzer

bump

fleabag

You've got a vacuum leak, one thing I'd suggest doing is removing and replacing the PCV valve and the rubber grommet which is likely all hard and crusty. You'll have to go over the engine bay and try to spot the vacuum leak but it's clear that your IACV is functioning properly. Check all the vacuum hoses to make sure they're not brittle and cracking on the ends of them. If you've ever done work where you've removed the fuel injectors, you could easily have a vacuum leak down there as well.

blazzer

so checked injectors. confirmed no vacuum leak.

i did notice on one of the vacuum hoses the very end was slightly melted. so maybe that is a casue. either way from a maintenance point of view, im gonna replace the pcv and this vacuum hose and see. incredibly small and i cannot believe i have missed this like 3-4 times going over vacuum hoses.

gonna feel so bad if that was the problem.

BTW

part # 17130-PM6-G01 (pcv) from honda in canada is 50$!!!!!!!!!!!!

im gonna try out one from napa. i am having a hard time justifying 50$ for a pcv valve.

ill post up if the vacuum hose and/or the pcv was a fix or not.

up to this point thnx all for the help... cant tell you how many threads i have gone through reading abut these problems

blazzer

OK so i "replaced" and confirmed no vacuum leaks. Replaced PCV just cause and well why not.

engine is still hunting.

it only seems to hunt when the throttle pulley is touched in any way and now it NEVER or very rarely goes to an idle under 1000 rpm unless i push the throttle pulley back.

Idle adjustment is still impossible wont go under 600 rpm

wonder if i should just buy a new throttle body??