987687 Posted December 14, 2013 Share Posted December 14, 2013 I have an annoying problem with my 89 GL (with ea81), but the ea82 efi system. Oh, and auto to manual conversion. The idle is random. When I start it cold (it's been below zero F here for a few days...) it'll idle above 2k. Even in the summer it'll do this. But once it's warmed up, it randomly chooses to idle between, say, 500 rpm and 2500. It's REALLY annoying. Sometimes when I shift it'll jump up to 4k, and then come down, sometimes when I stop it'll nearly redline and SLOWLY creep down to 2k, and just sit there. Sometimes it'll drop right down to 700, sometimes it almost stalls.... I'm pretty sure I don't have any vacuum leaks. I don't have EGR or the other emissions crap hooked up. And no other hoses are leaking. Due to the ea81 swap, the IACV is upside down. This car has always done annoying things with the idle, but it seems to be getting worse. I dunno if that has anything to do with it. Other than running OBSCENELY rich during open loop warming up, it seems to run somewhat decently. And yes, timing is set to 20 dbtdc with the green connectors hooked up. Link to comment Share on other sites More sharing options...
naru Posted December 14, 2013 Share Posted December 14, 2013 Sounds like. Try unplugging it or blocking the inlet tube after the motor warms up.See what happens. Link to comment Share on other sites More sharing options...
987687 Posted December 16, 2013 Author Share Posted December 16, 2013 If I unplug the harness connector, the idle drops fairly low. If I also crimp the vacuum hose closed the idle drops slightly lower. With the iacv unplugged the engine will immediately die over about 3/4 throttle. It's like unplugging the ignition. This doesn't really make any sense to me. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 16, 2013 Share Posted December 16, 2013 Definately doesn't make sense. The plug to the IACV is a simple 12v power source for a heating element in the valve. When its cold the valve is open, but as it heats up it shuts down. It's a valve that's only use is to bypass air around the TB when cold to raise the idle. So unplugging it shouldn't have anything to do with reving past 3/4 throttle. The coolant temp sensor controls when this valve gets 12v. Maybe you should start looking into that? The plug connection gets corroded, so that could be your issue, or the sensor itself. Mine was bad, and it gave me a wonky idle and overall I was running rich. Link to comment Share on other sites More sharing options...
987687 Posted December 16, 2013 Author Share Posted December 16, 2013 It's funny you mention the CTS, I was thinking about that sitting in traffic stuck with a 1500rpm idle. Has anyone listed resistances for the CTS under normal conditions? Warmed up, cold, etc so I can put a meter on there and see if I get expected readings? The wiring on this car does have gremlins, so it could very well be corrosion. Do you know how the IACV works? I assume it's just a PWM signal, but I don't feel like dragging my oscilloscope out into the apartment parking lot in the snow. Seeing as the idle dropped down immediately unplugging the thing, I can pretty much conclude it's not sticking open, so the computer is telling it to idle high for whatever reason. I figure cutting gas has something to do with the fact it's missing a part of the control system, computer is probably unhappy. I bet if I made a dummy load it wouldn't care. It's supposed to be 10 below tonight and windy. Since I live on the river it's unlikely I'm gonna want to go outside and mess with it tomorrow... but weirder things have happened. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 16, 2013 Share Posted December 16, 2013 I can't say for sure how the subaru unit works, but I can tell you how I fixed mine. I have the ea82t so I have the one that's mounted on top of the thermostat. I busted mine testing it cause I'm hard on parts... So I ended up using a IACV from a vw. The concept it the same, and its worked great. Even in the single digit temps we've had lately. I wired in the 12v plug, connected the hoses, and it works great. High idle when cold is 1200-1400, then it drops down to 800-900. The vw unit has a bimetal strip that heats up when 12v is applied, and it that shuts the valve. I'll assume the subaru unit works similarly. I don't know if the ecu needs to see any resistance from it, I'd assume no. Link to comment Share on other sites More sharing options...
987687 Posted December 16, 2013 Author Share Posted December 16, 2013 well it must check if there's a load there, because it completely dies from any RPM, in neutral or in gear going down the road over 3/4 throttle. It's like hitting an off switch. What kind of vw did you get it from? Link to comment Share on other sites More sharing options...
CarpeNoctem Posted December 16, 2013 Share Posted December 16, 2013 If it's cutting fuel at 3/4 throttle and has bad idle check and clean you MAF sensor with MAF sensor cleaner (use the right stuff it matters). I just had this issue and now it's MUCH better. Next I'm cleaning my IAC up and replacing the CTS. Link to comment Share on other sites More sharing options...
987687 Posted December 16, 2013 Author Share Posted December 16, 2013 It works fine when the iacv is plugged in, though. The cutting out thing is directly related to unplugging it. It runs mostly fine when I'm driving, so I doubt it's the MAF. Although I do have some MAF cleaner at my parents' house. I have to go see them for christmas, so I'll grab a spare maf and that out of storage... Link to comment Share on other sites More sharing options...
naru Posted December 16, 2013 Share Posted December 16, 2013 Probably dies at 3/4 throttle because the computer is in fail safe mode. Bet it doesn`t die at 3/4 w/you disable the IACV by blocking the tube and leaving it plugged in. IACV needs a good cleaning,IMO. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 well it must check if there's a load there, because it completely dies from any RPM, in neutral or in gear going down the road over 3/4 throttle. It's like hitting an off switch. What kind of vw did you get it from? http://www.ultimatesubaru.org/forum/topic/141806-aaviacv-questions/?fromsearch=1 Link to comment Share on other sites More sharing options...
987687 Posted December 17, 2013 Author Share Posted December 17, 2013 Cool, thanks. I can find that easier in a junkyard than GL/loyale parts. Those have all long since rusted out and been crushed. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 where are you from in northern maine? i grew up in fort kent/van buren. Link to comment Share on other sites More sharing options...
987687 Posted December 17, 2013 Author Share Posted December 17, 2013 I'm being a poser, I'm not actually in northen maine. I'm in Orono... Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 Haha, I lived on Forrest ave in Orono when I went to Umaine. Link to comment Share on other sites More sharing options...
naru Posted December 17, 2013 Share Posted December 17, 2013 Definately doesn't make sense. The plug to the IACV is a simple 12v power source for a heating element in the valve. When its cold the valve is open, but as it heats up it shuts down. It's a valve that's only use is to bypass air around the TB when cold to raise the idle. So unplugging it shouldn't have anything to do with reving past 3/4 throttle. The coolant temp sensor controls when this valve gets 12v. Maybe you should start looking into that? The plug connection gets corroded, so that could be your issue, or the sensor itself. Mine was bad, and it gave me a wonky idle and overall I was running rich. You are confusing the Auxilary air valve on yor MPI w/the IACV on SPIs. A simple AAV will not work w/a SPFI ECU. Coolant sensor has no effect on an AAV.It gets 12V all the time. Idle RPM is feedback controlled by the SPFI ECM. Not so for MPI. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 I didn't realize there was a difference between the 2, spfi and mpfi. I've never had a spfi, I'm using an aav on my mpfi. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 Seriously though, why would subaru have 2 different systems for idle control between the spfi and mpfi? Link to comment Share on other sites More sharing options...
987687 Posted December 17, 2013 Author Share Posted December 17, 2013 Because it's an entirely different setup. One has a turbo and all sorts of different things, and one doesn't. Look at turbo vs n/a EJ cars, everything is different. Now back to the situation at hand.... Since when I unplug the iacv the idle drops way down, I can assume it's not sticking and that the computer is telling it to idle high. What gives. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 After thinking about it, it's probably cause the injector for the spfi is in the throttle body. You can't just bypass air around the TB to raise the idle like an aav would. The air wouldn't have any fuel mix and it would be lean.... Link to comment Share on other sites More sharing options...
987687 Posted December 17, 2013 Author Share Posted December 17, 2013 (edited) What? No. Go look at how a MPFI ej engine works. The injectors are right at the bottom of the intake manifold by the heads. And the iacv is either mounted to the side of the intake manifold just after the throttle body (phase 1), or part of the throttle body on phase 2. But that's all completely irrelevant because I don't own a newgen car that works anymore. So back to the old school. And actually some of the early ej18s have a wonky setup like what you're describing about the turbo ea82. Edited December 17, 2013 by 987687 Link to comment Share on other sites More sharing options...
86 Wonder Wedge Posted December 17, 2013 Share Posted December 17, 2013 After thinking about it, it's probably cause the injector for the spfi is in the throttle body. You can't just bypass air around the TB to raise the idle like an aav would. The air wouldn't have any fuel mix and it would be lean... This is exactly what ANY idle valve does. Before DBW, (and after carbs) most systems would close the throttle plate completely allowing for almost NO air to flow through it. This valve is a metered air leak, essentially, after the throttle plate to allow the engine to draw air in. The IACV on the SPFI systems (Subaru specifically), the IACV opens when the TPS hits the "idle" circuit (throttle is at 0 opening). When the throttle is opened past a certain point, the circuit opens, then valve closes and cuts of air because there is enough of an opening in the throttle plate. I'd check the adjustment of the TPS sensor. There are 2 screws that anchor it to the throttle body and allow for adjustment. Make sure the "idle" circuit is not opening any time except at idle. Check to make sure the "opening zone" is within spec. I'd also make sure your throttle plate is snapping shut and/or completely closing. Gunk build-up from sitting or lack of use and cause the plate to stick or not seat properly. Lastly, I'd make sure the throttle plate shaft does not have any axial play relative to the throttle body. I've seen this happen on high-mileage stuff (causing a vacuum leak randomly or erratic running/idle). Link to comment Share on other sites More sharing options...
987687 Posted December 17, 2013 Author Share Posted December 17, 2013 Is it a rheostat type TPS on these, or is it the kind that only registers at idle, mid throttle, and WOT? When I go near WOT I hear a relay under the dash click. And if the IACV is unplugged, the motor dies at the exact same time. If it's a rheostat type tps it probably needs to be cleaned... Seeing as unplugging the IACV drops the idle down to 500 warm, I can only imagine the throttle plate is closing. But I'll give it a double check. I cleaned all that spoob out over the summer. Link to comment Share on other sites More sharing options...
mr sarcastic Posted December 17, 2013 Share Posted December 17, 2013 The click you hear is the wot switch on your pedal assembly. So, on spfi the IACV controls idle at operating temp. I'm fimiliar with this, style, many of the cars I've worked on in the past have these. On mpfi, the aav only controls idle on cold starts. It's open or closed based off temp... So what controls idle at operating temp on mpfi? What controls cold start idle on spfi? I guess my real question is why would subaru have to different systems for this? I don't care that ones turbo and one isn't, many manufacturers have turbo and non turbo cars that share almost the same FI. Just larger injectors, maps, ect. Link to comment Share on other sites More sharing options...
987687 Posted December 17, 2013 Author Share Posted December 17, 2013 (edited) Sorry, I really don't care how turbo ea cars work. I'm probably never gonna own one, and it's really not relevant to the issue I have with my n/a. They likely changed it because there was no way to fit the other valve on the intake or something, I dunno. It's different, yay. Edited December 17, 2013 by 987687 Link to comment Share on other sites More sharing options...
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