oregonloyale Posted November 27, 2003 Share Posted November 27, 2003 I recently bought a 93 legacy wagon AWD from some folks for $2999 here in oregon and when I was test driving it everything was great (140k on odometer). 1 day after buying it wife is sitting @ stop loght and it just dies. Today I am driving it , stop at a light , turn on defrost/heat setting and notice the tach bounce alittle low. I then push the defrost button and it just dies! Here is a list of things that have been replaced on the car in the last 2years and 30k miles.... 109k = new starter 110k = new rear brakes 120k = new H2O pump and t -belts and pulleys 126k = new frt CV's 136k = new AAMCO trans. 140K = new alternator also new fuel filter , sprk plugs , spark wires and air filter. Could this stalling problem be that the alternator belt is to tight and or the clutch on the AC is binding when it engages in defrost mode or is it a problem with the IAC? :boohoo: Link to comment Share on other sites More sharing options...
DerFahrer Posted November 28, 2003 Share Posted November 28, 2003 Your IAC valve will not let the car idle at all if it's malfunctioning. It will just stall no matter what. Unless of course, the stopscrew on the throttle body has been moved to create a makeshift idle... Tell ya what. Find the screw, it's very close to where the throttle cable attaches to the throttle body. Tighten it some, then turn your A/C on. If the idle , but will still run, after you have played with the screw, then, yes it is your IAC valve... If that doesn't work, I'd check your A/C compressor for lack of oil or something... or maybe a problem with the clutch... Link to comment Share on other sites More sharing options...
oregonloyale Posted November 28, 2003 Author Share Posted November 28, 2003 I forgot to mention its a auto tranny., if that matters. It only happens at an idle and very erratically , amybe 1 out of 3 times. And only with the defrost or the heat/defrost button engaged. It doesnt do it on any other climate setting. I do not know if it does it on A/C setting as I havent tested that one yet. It seems to idle at the normal rpms when 600-800 during normal idle and when you turn on the defrost it idles at 800-1000 for a little bit maybe 5-15 seconds then stalls. Link to comment Share on other sites More sharing options...
alias20035 Posted November 28, 2003 Share Posted November 28, 2003 Originally posted by oregonloyale I forgot to mention its a auto tranny., if that matters. It only happens at an idle and very erratically , amybe 1 out of 3 times. And only with the defrost or the heat/defrost button engaged. It doesnt do it on any other climate setting. I do not know if it does it on A/C setting as I havent tested that one yet. It seems to idle at the normal rpms when 600-800 during normal idle and when you turn on the defrost it idles at 800-1000 for a little bit maybe 5-15 seconds then stalls. My IAC died in a similar manner. When the AC cuts in, the ECU opens the IAC to increase idle RPM's by 150-200 rpm or so. The IAC malfunctions and closes, stalling the engine, and sometimes it will start to work again just before the engine dies, and the idle speed starts jumping erratically. IAC failures are a common item on 89-94 Legacy's. I removed my IAC and cleaned it with brake cleaner, and had no further problems with it. You might try the same. Mark its installation position, remove the two screws and electrical harness. Clean the top, the valve and the intake where the valve sits. The IAC uses an electro magnet to open and close the valve by rotating it, or at least it did on my 93 Legacy wgn 5MT. 4EAT's have a few different components, but I don't think the IAC is one of them. A/C compressors rarely seize, unless there is physical damage to the clutch assembly or the pressure swith is stuck in a closed state. The pressure switch is designed to protect the compressor and is supposed to open if refridgerent pressure is too low and not allow the compressor to run. Sometimes the pressure switch gets stuck in either an open or closed state. If you A/C does work (cold air) and doesn't make a horrendous sound your A/C compressor is fine. Check for cold air, and note if the A/C compressor cycle times increase at a high fan speed as compared to a low one. As more air moves through the evaporator, the compressor should cycle more often to maintain its cold temperature. You can eliminate the A/C compressor as a cause easily by disconnecting the clutch wire on the top of the compressor. The ECU will still try to raise the idle RPM but the A/C compressor will not engage. If you still have idle/running problems, it is not the A/C compressors fault..... If the problem is solved, then maybe the compressor is seized (but the pressure switch should have prevented this). You can leave the clutch wire off until you get the A/C serviced to prevent stalling. Link to comment Share on other sites More sharing options...
Legacy777 Posted November 28, 2003 Share Posted November 28, 2003 don't touch the throttle stop screw......clean the IAC valve.....if you still have problems, check the IAC valve Link to comment Share on other sites More sharing options...
oregonloyale Posted November 28, 2003 Author Share Posted November 28, 2003 Now the wife says it is idleing low and almost stalling during normal operation.I bet its the IAC getting gummed up . I will not mess with the throttle stop screw, but I am going to do the old brake cleaner in the IAC techniqe this weekend.' Ill post the outcome of this on monday. Link to comment Share on other sites More sharing options...
jimscat Posted November 30, 2003 Share Posted November 30, 2003 I have similiar issues with my 93. What is the IAC? 1 Link to comment Share on other sites More sharing options...
alias20035 Posted November 30, 2003 Share Posted November 30, 2003 Originally posted by jimscat I have similiar issues with my 93. What is the IAC? Idle Air Control It is a magnetically controlled valve controlled by the Electronic Control Unit (ECU) to allow air into the engine when the throttle is closed. Since fuel is pumped in to match the air sucked in, the ECU is able to adjust how open the IAC is to control idle speed when your foot is off the accerator and the throttle plate is closed. It replaces the idle speed set screw (screw to set minimum throttle opening) and cold operation idle adjuster that are present on carburators. Some less sophisticated fuel injected cars still use a screw type idle adjuster, but the Subaru EJ series engine was state of the art when introduced in 1989 and in almost all respects still is today. The IAC is located on the left side of the throttle body (looking from the front), it has a round top and has a wiring harness. When the IAC is dirty or defective, it can be slow to respond and not open in time to prevent stalling when you release the accelerator pedal. It can also malfunction when the ECU tries to open it to raise idle speed when the A/C cuts in. Link to comment Share on other sites More sharing options...
alias20035 Posted November 30, 2003 Share Posted November 30, 2003 Hopefully someone can confirm my hypothesis on how the IAC works: 1. The vacuum of the intake manifold acts like a spring to rotate the IAC valve to a closed position. 2. The ECU sends pulses of electical current to the magnetic cap over the IAC. The greater the frequency of the pulses, the more the IAC rotates open. This magnetic "opening" force counteracts the intake vacuum's "closing" force. 3. When no or low vacuum (throttle open) the valve rotates fully open, which is why the idle speed remains high for a second or so after the throttle is closed. The ECU probably opens the valve when the throttle is depressed and gradually closes it until the desired idle speed is obtained. This would prevent stalling and an abrupt change to idle speed. Its been seven years since I had my 93 Legacy's IAC apart, but I was very suprised to find that the valve seemed to be freely rotating component with no springs or the like and the cap was totally sealed. The cap does adjust, and I guess that this is to make fine adjustments to the idle speed. I marked my IAC with a paint pen before removal and replaced it in the exact same location. The above hypothesis would also explain why any minor contamination would cause problems. On my 93 the IAC was coated in a very fine film of engine oil, so probably at one point the oil was overfilled and some was sucked into the intake. I had also diagnosed a bad PCV valve shortly before my IAC problems. Link to comment Share on other sites More sharing options...
DerFahrer Posted November 30, 2003 Share Posted November 30, 2003 The IAC is not vacuum-operated to my knowledge. It works on the input from the ECU based on the TPS readings. When the TPS tells the ECU the throttle plate is closed, the ECU then tells the IAC to open. How I know: Josh did say not to touch the throttle stopscrew. While I was talking about the one on the top side of the throttle body, and not the one towards the bottom (do NOT touch that one for sure!), the truth is you shouldn't touch either, although the top is more forgiving than the bottom. Anyway, why you shouldn't touch them is because you are now altering the TPS signal and the ECU is now going to operate the IAC valve under new parameters. But still keep in mind: If the IAC valve is stuck closed with the aforementioned screws in factory positions, the car will not run at idle! Link to comment Share on other sites More sharing options...
Legacy777 Posted November 30, 2003 Share Posted November 30, 2003 yeah.....iac valve is not controlled or affected by vacuum. it's solely controlled by the ECU. I can watch the duty % of the IAC valve on my select monitor.....everythings handled by the ecu. Link to comment Share on other sites More sharing options...
alias20035 Posted December 1, 2003 Share Posted December 1, 2003 I didn't mean that the valve was vacuum actuated, just that vacuum within the intake will suck the IAC closed. I have had these apart and there is no spring, or apparent mechasim to precisely control the opening and closing of the valve. There is no "motor" to control the valve either, just apparentely a magnetic cap. Because of the limited number of wires on the IAC, there could not be multiple magnets within the IAC, so it must receive pulses from the ECU. By using pulses to open the valve, a spring would be required to close it, but there is no spring.... This is why I think the intake manifold vacuum or the air moving through the IAC conteracts the magnetic opening pulse from the ECU to close the valve or hold it at a precise opening point. I agree that you should not adjust the IAC unless properly trained on how to do so, which is why I recommend using a paint pen to mark its location prior to disassembly, so it can be reinstalled in the exact same position. I don't think the IAC is too sensitive to slight adjustment changes as the ECU does use other sensors to control idle speed (MAP/MAF, Crank angle sensor, etc). As far as I know the ECU will keep the IAC completely open until it decides to close it. Which is why the idle speed will be high for a brief period and then over a few seconds reduce. The IAC is kept open by default because it does not respond very quickly to ECU inputs. The IAC is fully open when the throttle is open, and I have measured this with my ODB tools. Link to comment Share on other sites More sharing options...
Legacy777 Posted December 1, 2003 Share Posted December 1, 2003 The whole cap is an electro magnet. the valve never is fully open or fully closed, it is always rotating open or closed, just how fast that is done is controlled by the ECU, and that electro magnet. I can pretty much guarantee you that vacuum is not sucking the valve closed. With the valve off the car, & cap still on, the valve is pretty much stuck half way open/closed. This is done by electro magnet top. Link to comment Share on other sites More sharing options...
frag Posted December 1, 2003 Share Posted December 1, 2003 thanks for the info guys. One can better understand why it's so easy for that valve to be sticking. No direct mechanical link to it just a magnetic field Do I understand correctly that it not the valve to throttle body position that's important to maintain but the relative positions of the mechanical and electrical parts of the valve? Link to comment Share on other sites More sharing options...
oregonloyale Posted December 1, 2003 Author Share Posted December 1, 2003 Alright back to my dilema...... I did the tests according to the haynes manual and I am recieving voltage at the terminals with the key in the on position = check And I started the car and allowed it to warm up to normal operating temp and then turned off car abd removed the IAC. haynes is incorrect in to things... 1 = there are 2 coolant hoses to remove not 1 2 = there are 4 bolts to remove the IAC body not 2 Anyways the manual said that after warm up and removal of the body the flap should be fully closed, not partially , well mine was half closed or open , however you look at it. I removed the magnetic/electrical part and marked it and then cleaned the IAC body w/brake cleaner. I then put it back together and ligned up the marks . When i lined up the marks it held the flap at half open again. I rotated the IAC one direction and this almost fully closed the flap. reinstalled the IAC and......... car still idles at correct rpms , around 800 but the car will dies upon activation of the heat/defrost switch or defrost switch but only sometimes , around 1 out of 5 times. sometimes I can hear wait sounds like a switch clicking on and or off from under the hood when I am in the car and the defrost/heat or defrost switch is actuated. I am just going to live with the inconsistencies of the auto for now as i have found the the legacy's are tempermental vehicles and so stuffed full of switches and selenoids , that it is almost impossible to ever have a 100% functioning ride. Dont get me wrong I love my Sube! Link to comment Share on other sites More sharing options...
Atomic Robot Posted December 1, 2003 Share Posted December 1, 2003 This may be totally off the mark, but my '93 Legacy was acting up in a similar way- stalling/clicking sound. It also became difficult to start- the problem ended up being a defective water temp sensor. Link to comment Share on other sites More sharing options...
alias20035 Posted December 1, 2003 Share Posted December 1, 2003 Originally posted by 93L This may be totally off the mark, but my '93 Legacy was acting up in a similar way- stalling/clicking sound. It also became difficult to start- the problem ended up being a defective water temp sensor. When my 93 had is stalling bouts there was a horrendous amount of clicking from the underdash area as it was stalling out. I cleaned the IAC and the problem never came back. Temp sensors are an extremely common failure..... Did you disconnect the A/C clutch wiring harness to rule out a seized A/C compressor? That should have been the first thing to do, perhaps it was not obvious in my previous post... Link to comment Share on other sites More sharing options...
oregonloyale Posted December 1, 2003 Author Share Posted December 1, 2003 does the AC clutch run when the defrost/heat or defrost mode is on ? Link to comment Share on other sites More sharing options...
alias20035 Posted December 1, 2003 Share Posted December 1, 2003 Originally posted by oregonloyale does the AC clutch run when the defrost/heat or defrost mode is on ? If will run in the heat/defrost and defrost mode when the air temp is above freezing..... The A/C will dehumidify the incoming air. Link to comment Share on other sites More sharing options...
GuerillaX Posted December 8, 2003 Share Posted December 8, 2003 I'm having the same stalling problems, gonna see if I can get to the IAC on my car, but just out of curiousity how much is a new IAC? I can't find it on any Subaru parts sites. Link to comment Share on other sites More sharing options...
alias20035 Posted December 9, 2003 Share Posted December 9, 2003 Originally posted by GuerillaX I'm having the same stalling problems, gonna see if I can get to the IAC on my car, but just out of curiousity how much is a new IAC? I can't find it on any Subaru parts sites. About $400 Canadian last time I looked in 97. I cleaned mine and my stalling problems disappeared. Does your car run ok with the throttle very slightly open? If so the IAC is likely to be the culprit, but also read further up in this thread to elimate the AC as a cause, and other potential culprits as well. Link to comment Share on other sites More sharing options...
oregonloyale Posted December 9, 2003 Author Share Posted December 9, 2003 Well my issue has to be my IAC valve as I disconnected the electrical part of my AC, black wire at top of AC compressor , and the car still stalled. Also after warming the car up to normal op temp. then turning it off , and then removing the IAc to check the condition . The Valve was half open. Haynes says this indicates faulty IAC. I cleaned the IAC with brake cleaner , reinstalled and problem still persist. BAD IAC, DAMNIT, and its christmas time !:boohoo: Link to comment Share on other sites More sharing options...
Legacy777 Posted December 10, 2003 Share Posted December 10, 2003 oregonloyale, What exactly does the Haynes manual say? The IAC valve is composed of two parts a bimetallic strip valve that is temp operated and an electromagnet rotary valve. The rotary valve portion will be and should be about half way open close. The bottom bimetallic valve should not be visible when warmed up. The bottom opening of the valve is where that temp based valve is located. I'll try and take some pics of the spare valve I have. Either way....if the temp valve was "failing" half open your idle would be higher then it should be because the valve is letting more air into the engine. Link to comment Share on other sites More sharing options...
legacy63 Posted July 7, 2006 Share Posted July 7, 2006 i have a 91 5mt ej22 did the same thing like legacy 777 said dont touch the stop screw it will only make matters worse and more expensive clean the I.A.C. also make sure the seal between the iac and intake is good. mine was not. fixed it with some gasket sealer. Link to comment Share on other sites More sharing options...
calebz Posted July 7, 2006 Share Posted July 7, 2006 Excellent use of the search. I applaude the fact that you are one of the few that can actually use it. However..... 2-3 year old threads can stay asleep for others to find with the search. Link to comment Share on other sites More sharing options...
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