peejay Posted February 19 Share Posted February 19 HI, there! The way I understand it, when the engine is cold, this valve is OPEN, to allow air to bypass the intake, and thus give a richer mixture? And when the engine (and the heater in the regulator) warm up, the shutter in the regulator closes, and now air is no longer bypassing the intake, but is instead going INTO the intake, to give a less rich mixture? But that doesn't seem right, because the way the regulator looks to be plumbed, it seems that when it's open, it allows air into the intake? Help me see things clearly, please! Link to comment Share on other sites More sharing options...
Slartibartfast Posted February 19 Share Posted February 19 It is built like an electric choke, but no, it does not mess with the mixture. Just the idle speed. The IACV raises the idle by giving the air blocked by the throttle an alternate path into the manifold (bypassing the throttle). This has the same effect as opening the throttle slightly. In fact the VG33 does exactly that, using a wax element (like what's in a thermostat) to prevent the throttle from closing fully when it's cold. Warm idle also bypasses the throttle body, but is controlled by the computer. I don't know why the two systems are separate. None of this should change the air/fuel ratio. The air that the IACV (or the thermo element) is letting into the intake manifold still has to go through the MAF sensor, so the computer knows about it, and will maintain the mixture accordingly. (Also, sorry for the radio silence on your wiring question--will get back to that soon!) 1 Link to comment Share on other sites More sharing options...
peejay Posted February 19 Author Share Posted February 19 Thanks as always, Slart! I kinda see it now, I didn't know it was metered air coming in, and your explanation of it bypassing the THROTTLE seals it. (Also, I've tabled the wiring thing...for now...exploring other worm holes!) Link to comment Share on other sites More sharing options...
adamzan Posted March 9 Share Posted March 9 I know on mine, on cold starts it stumbles and runs a bit weird but only when you touch the throttle, and it is 100% dependant on how cold it is. If it is -20 it will stumble and hesitate without doing anything, on a hot summer's day you might not even notice it. If you turn on the air con - slight misfire goes away. I replaced the valve under the plenum and it's better, but it still isn't right. Going to try and find an iacv-air regulator that is known good. Link to comment Share on other sites More sharing options...
peejay Posted March 9 Author Share Posted March 9 "Known good" always cracks me up, especially when it comes to the ECU. Like everybody has a known good, vehicle-specific ECU just laying around! Link to comment Share on other sites More sharing options...
adamzan Posted March 10 Share Posted March 10 I do have a known good 1994 SE Automatic ECU, lmao. 1 Link to comment Share on other sites More sharing options...
peejay Posted March 11 Author Share Posted March 11 22 hours ago, adamzan said: I do have a known good 1994 SE Automatic ECU, lmao. There just has to be that one forum member... Link to comment Share on other sites More sharing options...
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