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  #1  
Old 11-10-2008, 08:45 AM
 
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Default Idle Air Control Valve Symptoms?

I am under the impressoin my Idle Air Control Valve is causing my issues, and wanted more opinions.

If the car is started when it is cold outside, it will idle lower and lower until it dies. It takes multiple starts to get it going. When warm out, it starts fine.

After being driven a while, when in park or neutral, the idle is high. Considerably higher than when first started.

I can unplug the Idle Air Control Valve, and the car doen't change idle or anything. Everything operates as it did when it was plugged in before.

MAF/AMM checks out ok, as does oxygen sensor. Fuel pressure regulator seems fine too. Throttle body is clean and the car has a new flame trap and vacuum lines with no leaks as far as I can tell. Throttle Position Switch adjusted correctly, but hasn't been checked electrically yet.

I have the following codes:
2-2-1
2-3-1

Is the Idle Air Control valve causing all this by being stuck wide open at all times? Could it be letting too much unmetered air into the engine causing rough cold starts, and enrichment of the fuel mixture, activating fault codes?

Thanks for the opinions in advance!
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  #2  
Old 11-10-2008, 12:35 PM
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Default RE: Idle Air Control Valve Symptoms?

Is the throttle switch adjusted properly?
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  #3  
Old 11-10-2008, 01:01 PM
 
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Default RE: Idle Air Control Valve Symptoms?

Yes.
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  #4  
Old 11-10-2008, 02:03 PM
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Default RE: Idle Air Control Valve Symptoms?

Then maybe the idle motor is dead.
When the car is running when you go from drive to park the idle shoud go up about 300 RPM for a few seconds then drop down to about 800.
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  #5  
Old 11-10-2008, 05:47 PM
 
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Default RE: Idle Air Control Valve Symptoms?

Well, I unhooked the hoses to the Idle Air Control Valve, but left it plugged in. I turned the ignition on, sending 12v through the connector, into the valve. Nothing happened. I unplugged the valve from the connector. Nothing happened. I guess it's dead. How does the IAC get it's voltage? Where from? I am understanding that with voltage applied, it should open, and snap nearly closed when voltage is removed. That being the case, it appears to be stuck closed. OHM readings on the valve were good, at 8.2.
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  #6  
Old 11-10-2008, 08:16 PM
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Default RE: Idle Air Control Valve Symptoms?

It gets signal to active from the throttle switch.Thats why I asked if it was adjusted correctly.
You hear a click when you just darely move the throttle?
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  #7  
Old 11-10-2008, 08:40 PM
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Default RE: Idle Air Control Valve Symptoms?

OK...here's the simple answer. The IAC, as you probably know, only affects idle. When the throttle blade is open to any degree, the IAC has no effect. You are describing a textbook dead IAC. Yes, your Throttle Position Sensor needs to be adjusted correctly. You should pull your TB every third oil change or even more often and clean it thoroughly IMHO. As previously described, hold the TB to your ear and you should hear a distinct click just as the throttle blade moves. If you don't hear it, loosen the allen screws and try to adjust it so it does click just as the blade opens. After you feel comfortable the TPS is correctly adjusted try this. After the car is good and warmed up and idling too fast....take a pair of vise grips and clamp off the hose (either one) on the IAC and see if idle drops as you clamp harder. The ideal tool for this is a hose clamp pliers but vise grips will do if your hoses are in good shape. Assuming your idle drops, you may conclude your IAC is ill if not dead. I've had some success cleaning the IAC w/ carb cleaner and getting the crud out; early ones can actually be disassembled to be cleaned while later ones are pretty much sealed units. If cleaning doesn't work, make sure your contacts are clean and unbent on the plug. If every thing looks good, call Nick at fcpgroton.com (No I'm not a shill, Nick knows his Volvos and they have low prices on IAC's) because the IAC is dead most likely. There is an outside chance the idle circuit on your ecu is toast but go w/ the IAC first.
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Old 11-10-2008, 09:02 PM
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Default RE: Idle Air Control Valve Symptoms?

Quote:
ORIGINAL: swiftjustice44

After the car is good and warmed up and idling too fast....take a pair of vise grips and clamp off the hose (either one) on the IAC and see if idle drops as you clamp harder. The ideal tool for this is a hose clamp pliers but vise grips will do if your hoses are in good shape. Assuming your idle drops, you may conclude your IAC is ill if not dead.
Just to ask about this statement. Do you mean if the idle doesn't change the motor is dead?

Because the motor is supposed to stall if the hose is pinched while at idle. If the idle doesn't change the idle motor isn't working.
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  #9  
Old 11-11-2008, 07:46 AM
 
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Default RE: Idle Air Control Valve Symptoms?

I'll try the hose thing today.

The TPS is adjusted correctly.

With the ignition on I get 12v at the IAC connector, is that supposed to change when I open the throttle? Will the car have to be running for it to change? Thanks.

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Old 11-11-2008, 08:47 AM
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Default RE: Idle Air Control Valve Symptoms?

Yes when you first move the throttle that should cut the voltage. The idle motor turns off when the throttle is moved the slightest bit.
You should be able to test without the car running.
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Old 11-11-2008, 11:53 AM
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Default RE: Idle Air Control Valve Symptoms?

Since you have 12 volts at, I hope, terminal one on the IAC plug, the next step in fault tracing is to check the wiring from the IAC to terminal 9 on your ECM...you're looking for breaks and/or poor connections. You can ohm the IAC with the ignition OFF. Connect the ohm meter between terminals 1 and 2 on the IAC valve; it should read approx. 8 ohms. If it doesn't read close, try a new IAC. You can go to the ecu and check the resistance there also. With the ignition off, connect your ohm meter between pin 33 an pin 9. Again, it should read 8 ohms. If you get another reading...most likely you have a break in the wiring between pin #33 and the IAC. Finally, with everything connected, and the car idling, you can check voltage between ecu pin 33 and 5. The voltage should be between 7-10 volts. If you get 12 volts...a new IAC is your answer. Sounds involved, but I'm a big believer in fixing things rather than throwing parts on.
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  #12  
Old 11-11-2008, 02:31 PM
 
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Default RE: Idle Air Control Valve Symptoms?

Thanks a lot! I'll give all this a try. I need to do some more Air Mass Meter checks anyway...

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  #13  
Old 11-11-2008, 05:09 PM
 
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Default RE: Idle Air Control Valve Symptoms?

Well, I'm pretty sure the IAC valve is dead.

Now how about this:

Under LH2.4 System Electrical Tests for "Oxygen Sensor Wiring Harness", when I connect between 24 and ground with the Oxygen sensor connected I have NO CONTINUITY. The book says I SHOULD have continuity. It's a week or 2 old O2 sensor that checks out okay when I perform the Oxygen Sensor checks.

The Green wire that connects between tho Oxygen Sensor and pin 24 shows continuity when I connect a test lead to one end and the other at pin 24.

Whats that about?
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  #14  
Old 11-11-2008, 07:22 PM
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Default RE: Idle Air Control Valve Symptoms?

With the car running check power at the green wire after the car warms up. It should read between 0 and 12 volts. It will constantly sweep between 0 and 12 volts.
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  #15  
Old 11-11-2008, 07:47 PM
 
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Default RE: Idle Air Control Valve Symptoms?

I'll do that Wednsday and report back with what I find.

How fast should it sweep, or does that even matter?
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  #16  
Old 11-11-2008, 07:55 PM
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Default RE: Idle Air Control Valve Symptoms?

It will usually constantly sweep it will be hard to keep track of it.

But running lean will stay below 6 volts running rich will stay above 6 volts.
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  #17  
Old 11-12-2008, 03:54 PM
 
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Default RE: Idle Air Control Valve Symptoms?

Okay, maybe I'm not understanding this, am I supposed to disconnect the O2 sensor for this check? with it connected and the car running I get the fluctuating 0-1v of the O2 sensor...

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Old 11-12-2008, 04:42 PM
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Default RE: Idle Air Control Valve Symptoms?

Yes you do it with the car running. If you disconnect the sensor you should have a 5 volt refrence voltage.
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  #19  
Old 11-12-2008, 07:41 PM
 
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Default RE: Idle Air Control Valve Symptoms?

So, with the car warmed up and running, I disconnect the O2 sensor and check the voltage on the green wire, and I should see voltage sweeping between 0-12vdc? Is that correct?

What is this checking exactly?

Thanks!

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  #20  
Old 11-13-2008, 07:19 AM
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Default RE: Idle Air Control Valve Symptoms?

No you leave the sensor connected. Then it should sweep between 0 and 12 volts. Disconnected it should read 5 Volts.

When you read that you are seeing what the O2 sensor is telling the computer to do to adjust the amount of fuel being injected into the motor.

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Old 11-13-2008, 07:19 AM
 
 
 
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