lsvtec101

iTrader: (1)

Ok, i have a 99 civic EX and im getting a check engine light 1 long 4 short (14) OBDII. so i thought my IAC crapped out on me so i bought a brand new one. and i just installed and im getting the same exact engine code. now im stuck and i dont get it. if its saying the IAC is bad when there is a brand new one installed???????

93LSivic

Did you reset the ecu??

EE_Chris

Here is a different perspective: If the ECU commands a valve to open/close and in turn it expects some other sensor to give a different reading as a result but it fails to do so. Is the sensor bad or is was the valve? See what I'm gettin' at.

The ECU commands the IACV to arrive at some idle rpm. Lets say that the idle is at 1500rpm and the ECU is trying to bring the idle back down to 750rpm, so it does this by keeping the IACV closed for a longer period of time. Well, the ECU has commanded the IACV fully closed but the idle is not at 750rpm....does that mean the IACV is bad? Obviously not, but the ECU thinks it is because its not doing its job (as viewed by the ECU).

Joseph Davis

First, what is your idle like?

Second, you should always check all wiring that has to do with the circuit before you replace the part.

I don't know exactly how bitchy OBD2 is, but for OBD0/OBD1 you can just put a 1K resitor in place of the IACV, and the ECU doesn't know any different.

lsvtec101

iTrader: (1)

i reset my ecu and still get the code 14, and my idle is rough i have to give it gas to idle then after 5 mins it will idle on its own.. so where would i check next ?

norcalcrx

Check all your wireing in that circuit. Use an ohm meter to make sure all the wires have continuity from the iac to the ecu.

lsvtec101

iTrader: (1)

the IAC plug has 2 wires and they run into the stock harness? so i have to take all the black wrapping around all the wires and follow it all the way to my ECU???? thats a project is there any easier way?

Joseph Davis

An ohm meter makes following the wires all the way to your ECU very easy. Think about it.

lsvtec101

iTrader: (1)

thanks for the replys!! I just found this meter ..... is this the one i need?

now i want to test this where it plugs into the IAC? and where it plugs into the ECU?

Scott - 93HB Si

int3gra

i can see your address in that picture

lsvtec101

iTrader: (1)

how do i measure duty? with this meter?

wagonerd

Not to hijack your thread... But I
Having a similar problem.

If my iacv is plugged in I get super high idle, if not plugged in I get barely any idle.

The iacv seems to be working fine... I went so far as to jumper the leads on the iacv straight to the Ecu, no difference. Is there another sensor in the circuit that would cause the ecu to keep the iacv wide open when the engine is hot?

I'm only getting code 14, it's an obd0 d16a1.

wantboost

iTrader: (2)

You can't just jump the leads.,, put a 1k resistor across the connector and see if the code goes away...
A bad coolant temp sensor can cause idle issues and make the ECU think the iacv is bad

And why bump an almost 10 year old thread? Make a new one

wagonerd

What I meant is, the wiring on the car has been messed with, so I was trying to eliminate any wiring issues. Bypassing the chopped up harness and going straight to the ecu from the valve.

Haha I bumped an old thread because I'm on a phone and the date is too small to read!

wagonerd

Thanks for the help btw. I'll check the temp sensor.

turbohatch96y7

iTrader: (15)

Sometimes the valves get stuck open.

Did you set the base idle on the car yet?

Check the resistance across the iacv valve.

Check resistance from the ecu to the iacv connector on both leads.

Check for 12v on the yellow\blk wire.

The green wire is the pulsed negative from the ecu.

Buy a multimeter if you don't have one. Cheaper and faster repairs will arise from this magical machine.

wagonerd

I definitely know the valve is working... I can hear it click when I plug/unplug it, as well as the obvious sound of air rushing through the port and the idle raising and dropping. the problem is the ecu causing it to open all the time whenever it's plugged in... there's something wrong with the circuit, not the valve. I have disassembled it and cleaned it, made sure it sealed and operated correctly, and checked the resistance. it checks out good !00%.

so like I said the wiring harness is butchered. the colors aren't even right

I had already checked for a complete circuit from ecu to valve, but I re-routed it with new wires to bypass the harness just in case there was an ancillary connection hidden somewhere that might be causing the problem. the multimeter shows a connection from point a to point b but doesn't show if there's a point C !

what I really need is how the circuit logic works for the ECU to control the valve, so I can find out why the ecu thinks the valve should be wide open all the time.

turbohatch96y7

iTrader: (15)

the only time your ecu will keep you're iacv wide open all the time is if the settings in your ecu software is off.
do you have a stock ecu or chipped?

you didnt give me a reading off your iacv solenoid resistance so i take it you just looked at it and didnt put an ohm meter across it to verify proper resistance.

if you do have a chipped ecu check the idle settings and iacv settings.
also did you set the base idle with the iacv disconnected and the bypass screw?

wagonerd

yeah I did check the resistance, that was over a year ago, the last time I had time to work on it... so forgive me for not remembering the number!

I have two ecu's, both from wrecking yard 87 integras (engine is a browntop). switching them doesn't change anything, I don't have any reason to think either of them has been messed with.

I've set the idle about every way it's possible to!!!

if I set the idle when warm with the iacv disconnected, when I plug it in the engine revs over 2k and then starts surging.

wagonerd

oh yeah. did I mention that I have already, out of frustration, paid an ASE tech with 25 years experience to troubleshoot this piece of ****? he couldn't find an explanation either.