I bought a Honda Civic Haynes repair manual and it said there how to check if my IACV is bad cuz my car was throwing code 14 and 17 which points to my IACV and VSS vehicle speed sensor. The book said to use a multimeter and test the terminals on the IACV and if it gives around 12v then it's good and same with the harness in the car or the connector that connects to the IACV but when we tested it, it was giving us around 5 volts? why is that?

I really wnna get to the bottom of this so i'll know if i have to replace my IACV or somethin cuz my car is idling erraticly/shaky from cold start but when warm it's works fine? any suggestions guys? OH! and does my VSS affects how my car runs right now at all?

 

yeah its time for a new iac valve i need a new one as well =T

 

Then you don't need a new IACV. What you need is to find out why you're receiving only 5V. Maybe someone switched the wires or the ECU is bad.

 

5v is a common sensor reference voltage. Check your electrical connectors and make sure that the iacv is connected to the proper wires. You could possibly have the iacv connector and a sensor connector (for example TPS has a 5v reference) switched.

 

just replace it and see what happens. if it dont fix it take it back get money back. or buy brake parts cleaners and clean the one you have now and it will work. that or you have the connectors switched. their are 3 clips exactly the same back their and probably mixed them.

 

But if ECU was bad wouldn't it throw a code for that?

 

Would local parts store would have them? ie. Kragen, Autozone? and they accept returns for those? but i will tryto see if i mixed the connectors up thanks guys! OH and i recently just cleaned my IACV and FITV btw thinking those would solve my prob but it didn't lol

 

No. ECU throws codes for bad sensors. If the ECU itself is bad, it wouldn't throw codes (I don't think).

 

oh isee but is there any other way or symptoms that my ECU could be bad? Cuz i don't wnna replace it and turns out that's not the prob?

 

If you have a friend, have them switch ECUs. If not get one and then return it if that's not the problem.

 

I talked to 2 mechanics already and they told me both that it could be the ignition coil and i also did some research on symptoms for a bad ignition coil and they all said the same thing: engine will shake/rattle, won't go over 25 mph no matter how much u press the accelerator, will not struggle goin up hill. Idk is this right? any ideas bout this?

 

More information is needed.

What year Civic?
Was the IACV connector unplugged when you measured voltage?
What terminal/wire did you take the voltage measurement from?

 

You sure you have the right manual for the engine you have? My IACV has around 4.5v when the car isn't running so your IACV voltage might be fine.

 

The IACV is on the same main relay circuit as the fuel injectors. With the key in ON(II), the IACV connector should have 12V at the wire coming from the main relay.

 

So would low voltage indicate a bad relay?

 

I think if the voltage is really only 5V, then the fuel injectors would not work and the engine wouldn't run. How are you measuring voltage at the IACV connector?

 

Across the two terminals of the harness-side connector with key at ON. The manual just says there should be "battery voltage present" but it doesn't specify the amount.

 

What year Del Sol? Engine won't start?

Here's how to do the test. Unplug the IACV 2P connector. Measure voltage at the YEL/BLK wire terminal of the wire harness connector to body ground with the key in ON(II). You should measure about 12V.

 

No my car is running fine. I think it's a 92 b16 in a 94 si. But yeah i just had a look since this guy was having problems and the voltage was the same on the battery ground and ground wire.

 

it's a 1993 del sol and i did exactly what you said how to measure the voltage at the YEL/BLK wire terminal of the wire harness connector to body ground with the key in ON(II) and it was giving me 5.43v to be exact

 

Hey Ron, can you show the schematic where you see the injectors and IACV running off the same source (main relay)?

 

No problem. Pretty much the same for 92-00 Civics:

(EACV = IACV)

 

I assume that you also measure 5.4V at the YEL/BLK wire at the fuel injector connector? Do you instead measure 12V at fuse 31 (see circuit diagram above)?

 

Thanks Ron, you're a great help around here!

 

I apologize, I re-checked the voltages and the iacv connector power- battery neg is 11.5v and the connector power to connector neg is 5.4v. Grounding the neg causes the idle to bounce rapidly. As I said before, my car's running well so I'd think this is normal.