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Discussion Starter #1
Hi all,

You may have read my "Thinking of selling my car" thread from a few weeks ago. Well I have had some time to put it out of mind, cool down, and think more clearly, and now I am trying to get it running again.

A few weeks ago I was driving it to work and it began to stall out as soon as I let my foot off of the throttle, I had to drive home with two feet and even then it was running really rough. This weekend I tried to start it again, it ran terribly and threw two check engine codes, faulty AFM code and faulty idle air control valve code. I assumed that one code was legit and the other (afm code) was going off from the other fault. I cleaned out the AFM with some specific AFM cleaner and removed and cleaned the idle air control valve.

I am now able to get it running but at idle it is jumpy. It will idle up a few hundred rpm all on its own and then back down again, and if I rev it up, instead of returning back to normal idle it will just fall and then stall out.
I have inspected all of the rubber lines and hoses and all looks good, I replaced the TPS switch a few years back and am hoping that is not the issue. I am thinking either failed or failing idle air control valve or possibly bad ECU temp sensor.

Does anyone have any other ideas? Or can anyone tell me what feeds information to the idle air control valve? i.e. what tells it to change parameters to keep a good clean idle?

As always any information is much appreciated.

Steve,
 

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I doubt it's a bad temp sensor. If those values are way out of parameters, then I believe a default value gets inserted.

I would check the Min-Max Switch. Preferably with an ohm meter to make sure it's good and operating correctly.

You also might try plugging off the vacuum line to the Evaporator Solenoid Valve just to eliminate that as a source of a big vacuum leak.

That said, I believe the problem is a bad/intermittent Idle Stabilizer/Idle Air Control Valve. Mine failed and never even threw a code.

http://www.alfabb.com/bb/forums/164-168-1991-1995/206282-diagnosis-idle-faults-164-a.html
 

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If min/max throttle switch set correctly 0<1 degree clicks on/off and evaporative cannistor solenoid not the issue then I guess if you have good Bosch connector to Idle Actuator Control (IAC) it is probably a bad IAC. I have spare extra ones if needed.
 

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Most of my fault code/idle issues have always been IAC issues. I have several used IACs on hand, they are the exact same as my '89 240 Volvo so a good reason to have 5-6 used examples on the shelf. If I have an issue with poor running, I swap in another and it usually does the trick. I mark the bad one as such of course so it can become a paperweight, dust collector, waste of space. :bored: I don't think it does much good to clean the inside of one of these vane type AFMs really. I did notice a difference though cleaning the contacts of the innards of the AFM (under the black cover, use alcohol & Q-tip). The motor became slightly sweeter running all the way around, but that's just for tweaking a little something more, not likely your problem here.
Charles
 

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Hey Steve,

I have a brand new ICV as a spare part... that I want to keep :) If you want, stop by my place and swap your existing ICV with mine for testing purposes. Replacement shouldn't take more than 15 min.

Best,
Sasha
 

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Discussion Starter #6 (Edited)
Hi Sasha,

Thanks for the offer but I don't think the car would even make the ride as of right now. If I start it it will idle smoothly but erratically idle up periodically, if I then give it some gas and let off of the throttle the rpms will just drop and it will stall.

After checking both the currently installed TPS switch and the spare that I have with an ohms meter (they both tested fine), and checking the voltage at the IAC plug (also fine), I am fairly confident that my problem is in fact caused by the idle air control valve.

I am going to check a few other things this evening and them probably reach out to Alfisto Steve for one of his spares.

Thanks again, Steve
 

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Discussion Starter #7
Bosch IAC manufacturing defect

My new Bosch IAC came in today and I am a little disappointed in Bosch's quality control. If you look at the attached pictures the metal baffle part of the valve seems to be a little crooked and I am thinking that this may negatively affect the function of the valve. I am going to assume that if the valve cannot close and open fully, and correctly control the amount of airflow into the intake, the car will not idle right. Any other thoughts on this?

I was really hoping to get the car up and running this weekend and don't want to ship the IAC valve back for another one if I don't have too. I also don't want to install it if tit will not work correctly.
 

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That may be normal, and it doesn't matter anyway. The ECU is going to command the stepper motor inside to open the shutter just wide enough to allow the right amount of air in to stabilize the idle at the desired rpm.
 

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You do know IAC valve moves vane to close opening shown in picture then there is another opening on other side. Just roll vance and set that it is free to move and spring tension snas it back to like your picture. If it moves freely and snaps back to this no power position I would give it a test on the car.

Also inspect closely the 2-wire connector you attach to it and be sure wire terminals locked in place and will clamp tightly to terminals in IAC.

Test valve with connector connected and turn on ignitiion key to see vane move.
 

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Discussion Starter #11 (Edited)
Thanks for the quick responses. It seems to be that the consensus among the experts is that this is not an issue. This one just seemed to be a little off from the original one that I removed. As soon as I get the time I will install the new IAC and report back.

Thanks again, Steve
 

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Discussion Starter #12 (Edited)
I finally had the time to install the new IAC, properly adjust the TPS switch with an ohm meter, put it all back together and fire it up, and it runs and idles great. I really should have replaced the the IAC a long time ago. I have had trouble with it for years with a bumpy idle and over-correcting causing the car to idle too low and then too high.

I would definitely suggest that anyone with a low or bumpy idle check their IAC, replace if bad, and adjust the TPS switch correctly using an ohm meter.
 

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Discussion Starter #14
Idle Update

Hi all,

I thought I would give an update and pick some of your brains as to the idle issue that I am now having. I haven't been working on or driving the car much lately because I have been so busy and I am still having a mild rough idle issue.

Since I started this thread to address the above discussed idle issue, I have replaced the IAC, spark plugs, cap and rotor, O2 sensor, adjusted the TPS switch, and checked the coil resistance. The original issue was that the car would not stay running at idle, it is now running at idle but with the occasional (every few seconds) misfire. Other than the misfire at idle the car is running really well. It idles relatively smoothly, the IAC is definitely functioning correctly because the idle fluctuates smoothly and regularly especially with the A/C on, it is smoother than it ever has been throughout the rev range, and it also has plenty of power on acceleration.

My father, who has been a mechanic for over 30 years, but admittedly gave up on Alfas a long time ago, thinks it sounds like a lean idle issues, possibly caused by a vacuum leak. Considering everything else that I have checked and replaced, confidently ruling out an ignition issue for the most part, this sounds like a promising place to start looking. Then I was thinking, if the original rubber boot that seals the IAC to the intake had aged and formed to the original IAC, would disturbing it and using it with the new IAC possibly cause a vacuum leak? I am also thinking that my original assessment of the new IAC and its slightly crooked internal baffle (pictures above) could be causing the same issue, too much air at idle.

Any ideas or suggestions as to what my issue could be or where I should start looking?

Thank you, Steve
 

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Your IAC is the way it should be and the way they all are as has been confirmed by several of us so you can give that a rest already. :blink: The vain rotates around and closes when/if it needs to.

I have had similar issues as you and I agree a VERY thorough tracking down of ALL the vacuum lines will likely find your issue. The IAC gasket can get shrunken and a wrap or three of it with electrical tape will snug it up. Very hard to find a new one. They have been known to cause a false air problem. Also, hunt down the vacuum lines that go down to the vacuum tank in the front driver's side wheel well. Make sure no lines have come disconnected (or are bad/split) and the caps that might be there on unused nipples are present as well. Make sure the tank holds vacuum. Track down your false air issue wherever it may be. You can also just remove vacuum lines to the cruise, etc just to check for leaks.

Make sure all your injector connectors are clean as well as that can cause an intermittent cylinder misfire.
Charles
 

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On ours the air bleed hose from upstream of the throttle plate connecting the intake hose to the AIC circuit, bypassing the throttle plate, popped loose intermittently. The connector is a short piece of stainless steel tube without ridges but secured by hose clamps. It can seep oily air which lubes it and then it can pop in and out intermittently. On my car it was the hose closest to the AMM but I understand this can differ from car to car as there are two very similar hoses.
 
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