spiff Posted September 17, 2013 Share Posted September 17, 2013 83 ZX turbo engine, euro model: I can't get the idle low enough, the idle adjustment screw is screwed all the way in, but still it idles at 1500rpms when warm. What it does is this; when starting from cold it will idle at around 1500 rpms and will settle down to about 800 when warm. So far so good right? If i drive it or rev it then it will all of a sudden idle at 1500rpms again. Today I started the car, backed it out of the garage and then left it to idle while I swept the floor and did some general cleanup, high idle when cold and then settling as it warmed up but then after a while it just jumped up to 1500, like flicking a switch. I pulled out some vice grips and started clamping hoses, when I clamped the hoses I'm pointing at with my screwdriver on the pictures the idle will go down to where it should be. (as no air is bypassing the idle valve) So what is the thing at the end of the hose, screwed in to the intake runner? I can't find it in the service manual, can't figure out what it does, other than letting extra air into the plenum and bumping up the idle seriously! Can I just unscrew it and plug the hole? Quote Link to comment Share on other sites More sharing options...
Chris83zxt Posted September 17, 2013 Share Posted September 17, 2013 (edited) TonyD will verbally slap me upside the head for not calling it what it is in the FSM, but it's basically a pressure relief valve that operates similarly to how a recirculating BOV operates. When the throttle plate closes under boost and there is a significant difference in pressure between the J-pipe and the intake manifold, that thing is supposed to open up and allow the pressure in the J-pipe to balance with that of the intake manifold. I could see how it might cause a high idle if stuck partially open. I used two big rubber hose caps to close it and the feeder tube off when I installed a real BOV. Edited September 17, 2013 by Chris83zxt Quote Link to comment Share on other sites More sharing options...
spiff Posted September 18, 2013 Author Share Posted September 18, 2013 Thanks. I'll probably close it off somehow then. Quote Link to comment Share on other sites More sharing options...
Xnke Posted September 18, 2013 Share Posted September 18, 2013 That is the AAR, auxilary air recirculation valve. It's a compressor bypass valve that prevents turbocharger compressor damage. I'd not just block that off, if I was you. I'd either replace it, or block it off and use an external compressor bypass valve, as mentioned above. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 18, 2013 Share Posted September 18, 2013 (edited) The device to the LEFT in your first photo is the culprit. That is the AAR auxiliary air regulator, inside the round section is a disc with a shutter in it that opens when cold. If it gets gunned up it sticks, and does what you are seeing. As you see the hoses are all common, blocking the source upstream to the TB stops the airflow around he plate directly to the manifold. I believe he device in the #4 runner is the VCV - vacuum control valve, "factory blow off valve" or " bypass valve"... It doesn't open till 1 psi or so... Should b closed at idle (then again so shoud the AAR!) Cap the 15mm line to the AAR, and that shokd stop it till you can clean or replace he AAR. Edited September 18, 2013 by Tony D Quote Link to comment Share on other sites More sharing options...
cgsheen Posted September 18, 2013 Share Posted September 18, 2013 From the US FSM Quote Link to comment Share on other sites More sharing options...
spiff Posted September 18, 2013 Author Share Posted September 18, 2013 That is the AAR, auxilary air recirculation valve. It's a compressor bypass valve that prevents turbocharger compressor damage. I'd not just block that off, if I was you. I'd either replace it, or block it off and use an external compressor bypass valve, as mentioned above. No sweat, I plan on running a bov as soon as I get my intercooler an IC piping fitted and welded in place. Altough my Z24ET ran for two years without a bov and it didn't show any signs of damage, but that's a different discussion... The device to the LEFT in your first photo is the culprit. That is the AAR auxiliary air regulator, inside the round section is a disc with a shutter in it that opens when cold. If it gets gunned up it sticks, and does what you are seeing. As you see the hoses are all common, blocking the source upstream to the TB stops the airflow around he plate directly to the manifold. I believe he device in the #4 runner is the VCV - vacuum control valve, "factory blow off valve" or " bypass valve"... It doesn't open till 1 psi or so... Should b closed at idle (then again so shoud the AAR!) Cap the 15mm line to the AAR, and that shokd stop it till you can clean or replace he AAR. I doubt it: What it does is this; when starting from cold it will idle at around 1500 rpms and will settle down to about 800 when warm. Sounds like a pretty good indication that the Air regulator is working like it should. I clamped the hose going to and from the air regulator when the engine was all warmed up and it did nothing, but clamping the hose going to the vacuum control valve does have an effect as described in my first post. I have also tested enough of these air regulators to know that they do not open in a split-second or just because of a slight pressure change. Quote Link to comment Share on other sites More sharing options...
spiff Posted September 19, 2013 Author Share Posted September 19, 2013 Today I plugged the Vacuum control valve hose, problem solved. Thanks for the help Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 19, 2013 Share Posted September 19, 2013 Today I plugged the Vacuum control valve hose, problem solved. What did the valve control? In other words, what are you giving up with your simple "solution"? Quote Link to comment Share on other sites More sharing options...
Chris83zxt Posted September 19, 2013 Share Posted September 19, 2013 What did the valve control? In other words, what are you giving up with your simple "solution"? I sense rhetoric in action. Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 19, 2013 Share Posted September 19, 2013 Just forumizing. It's interesting to see how the path to "my engine doesn't run quite right" starts. Quote Link to comment Share on other sites More sharing options...
spiff Posted September 19, 2013 Author Share Posted September 19, 2013 Funny.... how you read any other post in this thread except for my last one? What did the valve control? In other words, what are you giving up with your simple "solution"? Just forumizing. It's interesting to see how the path to "my engine doesn't run quite right" starts. That is the AAR, auxilary air recirculation valve. It's a compressor bypass valve that prevents turbocharger compressor damage. I'd not just block that off, if I was you. I'd either replace it, or block it off and use an external compressor bypass valve, as mentioned above. TonyD will verbally slap me upside the head for not calling it what it is in the FSM, but it's basically a pressure relief valve that operates similarly to how a recirculating BOV operates. When the throttle plate closes under boost and there is a significant difference in pressure between the J-pipe and the intake manifold, that thing is supposed to open up and allow the pressure in the J-pipe to balance with that of the intake manifold. I could see how it might cause a high idle if stuck partially open. I used two big rubber hose caps to close it and the feeder tube off when I installed a real BOV. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 20, 2013 Share Posted September 20, 2013 Fix the valve don't just plug it. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted September 21, 2013 Share Posted September 21, 2013 Yep.....fix it if you're running the stock J-tube because it's there to relieve pressure that builds when you lift the throttle under boost. It's there for the benefit of turbo longeivity. If you're running an intercooler system, you could get away without that valve if you have a "blow off valve" plumbed in but I run both the factory valve and a blow off valve set to recirculate to the turbo inlet. Quote Link to comment Share on other sites More sharing options...
spiff Posted September 21, 2013 Author Share Posted September 21, 2013 Well it's not running at all at the moment as I have pulled the oil cooler and hoses trying to get some new hoses and fittings made up. But I have ordered an intercooler and one of those universal piping kits, have a bailey bov sitting infront of my pc which will go in when I get the piping and intercooler fitted and welded in place. Quote Link to comment Share on other sites More sharing options...
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