Idle air control valve IACV, idle speed control valve ISCV from 3sgte engine (MR2 and Celica)
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- เผยแพร่เมื่อ 8 ก.ย. 2024
- My "new" 70mm throttle-body (from a Lincoln LS) is lightweight, progressive, and simple in design... it has no through-passages or air bypass valves. When bolted to my redesigned intake manifold, I needed to have computer-controlled idle adjustment for cold startup. I am still on the stock 3sgte ecu for this year, so I made an adapter plate for my TPS (throttle position sensor) and a semi-remote mounting point for my IACV. Without the valve I had to hold my foot on the gas pedal a little during cold startup. Once warm, the car idled fine at 800 RPM. So, I needed to adjust the range of my IACV, and get it to close as much as possible, or my idle might be too high when warm. Now the valve will open on cold startup to give me a higher idle. I may re-adjust my idle stop screw and my TPS in the future to reduce my idle RPM's and give the IACV more control.
#iacv #iscv 3sgte
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Thanks for this video! This 3SGTE IACV looks pretty much identical to the one in the 4AGZE, so this has proven very useful !
You are welcome!
@@mkloppers With no voltages applied to your IACV - what position was it in? Open, closed or somewhere in between?
@@AE92World
good question. I actually considered using no ground as a “setting”, for something in between, but it is inconsistent and unreliable, as far as the position the valve relaxes in. You can actually see in the valve actuation before I adjusted it, that there is a moment that the valve “relaxes“ as I release the ground from one pin and switch to grounding the other pin, the valve relaxes slightly towards the centre from its last known position. So, after fully closed, it will open up a tiny bit and after fully open, it will close a tiny bit. After I adjusted the valve, it seemed to relax less with no ground applied, but I believe that air pressure (or vacuum) will likely push the valve to a partly open position in short order.
Thanks! My iacv is likely gummed up and stuck closed because i hardly have any rpm at cold start. Sits at like 500rpm and nearly dies. But once warm it's fine. Hoping a good clean will solve my low idle issue.
It sounds like yours is not opening at startup.
Mine did that again recently, and it was likely due to water-meth (WM) injection, as the location of the valve bypass tube in my setup allows it to possibly collect some WM, and the valve, once closed, would sit in WM overnight or however long before the car would be started again... I noticed the idle down was not as pronounced when I deactivated it, and this progressed over the course of a week or two, until it stopped closing altogether (RPM's would stay high after startup, and idle was permanently higher). I think it needs some periodic attention, seasonally perhaps, and certainly the moment the idle performance begins to change. An abrupt change one day to the next may indicate a problem other than gumming-up. I tuned it out until the next time I removed the valve, and then had to retune idle again once I got it moving again. During that stretch with the valve stuck open, there was a limit to how low I could drop my idle (by pulling fuel in the idle range) before the injectors would hate it and the idle quality suffered and didn't sound right/smooth.
@@mkloppers YES! I also run water/meth injection. I was thinking this could be a contributor to my low idle situation. Either way, it's probably best I pull the iacv off and have a good look.
thankyou you have really helped me out with this one, im going to check mine now
Thank you so much
Glad it helped out.
thanks for the vid. still useful in 2020. question. I have a thumb, or thud sound when im under boost, specially when I let of the gas. I can't figure out where the leak is coming from. I've replaced every vacuum hose but nothing. is there anything else I can check? theirs no loss in power or anything, boosts just fine but the noise is annoying, engine is stock. gen2 turbo
Vacuum/boost leaks won't likely produce the sound you describe... they usually squeal or are inaudible under the engine noise. A thump or a thud sound... I would check all the motor mounts, especially the front/rear, exhaust system, intercooler mounts etc. As you come off the throttle the engine rocks forward (and rocks backward with sudden hard acceleration), and something is making accidental contact with a part of the frame etc, or there is looseness that shows itself with the engine movement.
Any idea as to the location of the sound?
Martin Johann Kloppers. Thanks I’ll check all of that. The noise seems to come from the turbo area. But only when boost hits and the gas pedal is let off.
@@frnciscob1 It occurred to me that while you may not have a leak, you may have boost-induced movement of a silicone coupler or joiner in your turbo piping, clamps etc, so that it caves in as throttle is closed under boost etc.
Thanks for awesome video. This test is suitable for isc valve 3s-gte caldina gt-t?
I believe the valve is the same. It’s the way Toyota rolled.
Thanks for the awesome video, I have a few questions. My cold start sequence seems to not be working correct - I start the car and on cold start it idles at 1000 RPM instead of 1500 like it should on cold start. My warm idle is stable at the normal 800 rpm (after fixing the leaks that were coming from the same place as yours). So my cold start RPM is too low. How should I adjust the plate (full close or open as much as possible, if at all) to allow for a higher cold start RPM? Thanks in advance.
Yes you should see more idle range than that.
The IACV together with voltage from the ecu based on temp and other parameters, is the main factor in startup idle RPM.
Did you test the IACV when you were sealing it for leaks?
It likely is not actuating as far to the open range as possible and could be somewhat stuck, range-limited. You should get 500 RPM difference, (thereabouts, or more).
If you did test it and could see it open and close with good range similar to in the video, then you could try and adjust the plate (as viewed from the front looking at the screw heads/plate, just like in the video) in the counter-clockwise direction, which will shift it's range towards further open. You may find that your warm idle also increases though.
If you find that adjusting the plate (without un-installing the valve and therefore cannot see the range of movement of the valve itself) has little or no effect, it is likely gummed up and range-limited.
Hi hows it going mate, Iv got a MR2 MK3 (spyder), it always revs up a wee bit when changing gear, if I change gear at say 3000 revs.... as soon as I press the clutch the rev counter needle always goes up by about 250revs for a second then comes down again, (if that makes any sense.haha) Just wondered if you had any ideas what would cause it to do that? Iv cleaned the MAF sensor but its still just the same. thanks :)
A few things may be affecting that. It sounds a bit like rev hang, but I don't think it is a common or consistent Spyder issue, and it shouldn't be caused by computer-emission controlled annoyances that will come up with other brands.
Yes, the IACV could need a cleaning/testing. It could also be a vacuum leak. You can also test the TPS.
I took my idle apart and cleaned it but made no difference, I then unplugged the connector to it and the idle was normal, plugged it back in and it started hunting again, the ecu will come apart now to check for knackred fuses etc........ seems to be common
did you test its operation by supplying power/ground to the pins? and did you test to see what voltage patterns the ecu is sending to the iacv at the connector?
This way you can see if the ecu is telling the valve to intermittently close, thereby causing the idle to surge. If the ecu is purposely causing it, there could be other causes like coolant is low and air is in the coolant, confusing the ecu due to other sensor readings it is receiving. You/we just need to eliminate the iacv as a suspect definitively, and then move on. (If you have done this, please disregard :) )
So would this "range plate" be where one would attempt to correct a cold fast idle speed that is too high? 96 Honda Civic EX A/T. Mine has the coolant circulating through it and a bimetallic spring. Fast idle is around 1600 to 1800 rpm and supposed to be only 850 to 1000 with no electrical load and in park or neutral (150 to 300 higher than the idle of 700). It is getting very annoying. Would I rotate that range plate a bit CW until I get the correct fast idle speed? Thanks for your video an if you see this would be grateful for any comment.
I haven’t fooled around with the Honda version of the IAC/ISC valve, I would wager it is similar in most ways to the Toyota version, but I don’t know specifically how Honda controls that valve. If your warm idle is perfectly normal, then it kinda eliminates the possibility that you have a vacuum leak (unrelated to the valve), because your idle would be up across the board.
Secondly, usually if these idle valves become clogged and hampered in function, they will have loss of range and loss of response to temperature difference, to the point that they don’t move at all.
Thirdly, if the coolant passages were clogged, it shouldn’t affect the range of the idle valve, because when cold, the temperature would still begin at ambient no matter how much coolant was flowing, or even none.
There could be a temp sensor that determines coolant temperature that is sending signals that are out of range, eliciting a higher cold idle… but, unlikely.
I would remove the valve, clean it thoroughly, check it for leaks (because a leak there could allow more air into the intake manifold than intended),
Bench test it for range if you can,
And then test that plate movement and it’s affect on the idle. The reason I would try this last, is because turning it down may bring down your idle across the board, including warm idle.
Hope that helps.
@@mkloppers Thank you. I did test my ECT because I also suspected it could cause high idle but it looks like it is accurate when comparing my scan tool output to an actual thermometer. I removed the throttle body and the IACV and cleaned them pretty thoroughly previously and the car accelerated better but I had to turn the warm idle speed screw (no adjustment for fast idle) to get the car to idle at 700 after this. The fast idle remained too high. I will try cleaning it again but this time I'll remove the coils so I can spin the shaft and I'll also bench test the closing and opening under 12V power. If that doesn't work I'll see nothing else to try but adjusting that range plate, except for PCV valve and spark plug wires, cap, and rotor which I will do first. Thanks!
@@captainwho1
Wires cap and rotor shouldn’t have any effect on your cold idle being high, it would affect overall drive ability etc, pcv might however, or any other vacuum related things. You might be able to get the idle cold/hot where you want it by adjusting both that plate and the warm idle speed screw.
@@mkloppers Thanks for encouragement. The PCV is very suspicious because the hose going to intake man. seems to be collapsed somewhat. If there is a blockage in the PCV maybe that could happen. Not easy to get at in this car (dumb!). One of the spark plug wires is bad even though the car runs great. Over 2 MOhms!!, hard to get a stable reading. I wouldn't put it past this car to try to put more fuel/air in to compensate at cold startup, which could cause a high idle? I just want everything else to be right before attempting to nail down the idle issue, which will require adjusting those two things hopefully, once I have determined once and for all that the IACV is totally clean. I'm thinking I might try removing the coils and cleaning it in my ultrasonic cleaner. I haven't seen anyone try that. I saw in other people's vids that their valves were closer to being closed at room temp. than mine so I'm hopeful that is the problem, although nobody (including me) thought to measure the opening.
@@captainwho1 sounds like a decent plan. Do post an update here, how things turned out. My car really is a Honda/Toyota combo, and much of the tech/designs between the companies of that era were surprisingly similar.
Hey! I was wondering if you can give me any advice on my manual '91 Celica GT? It's dying on its own when I slow down/stop, unless I hold a mild rev on the gas to keep it from dying out. If it does die it won't start back up again at first. Pretty hot, I can see the heat lightly coming up from hood. Usually takes a few cranks, but within a half hr it has been starting up. I took it to an 'Oil Stop' and got a tune - up : Full Oil Service New Fuel Filter, Spark Plugs, Ignition Wires, Rotor and Distributor cap. Only note they added was "Cracked Air Intake Hose"Bought the car on a hunch for $750. It shakes a lot unless I go fast/keep at high RPM.
So your engine is a naturally aspirated 2.2L 5sfe, and your car is a North American model?
Coolant topped up and engine temps normal? Burning/using oil? Compression? Leaking fluids anywhere?
Assuming the above is normal/correct, first thing I would do is test for vacuum leaks. Replace that intake hose, you should be able to track down a used one from a wrecker for not much$.
I would get a hold of the service manual online for your car/engine. Join the celica forum. You can then do some basic testing (requiring a voltmeter) on a few items like the TPS (throttle position sensor). The IACV also needs testing. The Celica/MR2 forums offer great resources and help. Join them. Find a local wrecker that has pick&pull policy, and has a Celica or two.
For $750 it's a steal... really without me actually looking at it. late 80's early 90's Toyotas were the best built and over-engineered cars, period. It likely won't take much $, and with some effort it will run well.
I also have later model 5sfe (Camry) parts that may help, if it comes to that. email me at 3sgte @ mk15.ca
hi i would to ask i got idle issues my idle goes 1,500 when neutral sometimes the idle goes to 1thousand, i adjusted the back of the idle control valve i loosen the two screws and set it in fully closed, the idle goes smooth at no AC but when i turn on the AC the idle drops down to 600 when the compressor is engage. Question does it really needs to be closed i mean the setting on the back of the iacv? or should i have to set it a little bit open so that the air will pass through?
Part of the job of the IACV is to open more during AC-on so that your RPMs at idle stay relatively the same or increase somewhat ... so it is possible your IACV is not actuating. Did you test it? You may have changed its range by moving it to the position that provides fully closed, and this gets you a normal-ish idle, but then when you flip on the AC the IACV is not compensating/activating and your RPMs drop too low.
With the IACV working properly on a stock (oem) setup, yes you likely want to have it adjusted so that it never fully closes and allows for a decent idle.
The purpose for me to adjust mine to close fully pertains to my particular setup, with a Lincoln TB, since I was putting it on a switch.
Adjusting it should be a last resort especially if it was working properly previously at some point, and priority should be to test its operation, and eliminate other possible reasons for high idle (like a vacuum leak).
My method for diagnosing high idle issues or abnormal changes in idle:
-was something worked on or possibly disturbed/changed recently that may affect idle? Couplers, hoses, boost, turbo etc? if not, proceed to next step
-do a boost/vacuum leak test on everything... couplers, hoses, BOVs, turbo, intake manifold, gaskets, everything... Eliminate all leaks. Boost leak tester is easy to build using ABS, and carefully spray test areas with slightly soapy water (dish soap is fine)... avoid soaking electronics.
-try and clean the IACV internally with carb cleaner, if it improves a bit then you may be on the right track.
-test IACV operation as per the BGB. If I am contradicting the BGB, follow it, haha.
-remove the IACV and test it with voltage from a spare battery. If it is working properly and responding, you may have a wiring or ecu issue.
Sometimes there is a separate idle set-screw right on the TB itself, which limits how much the TB will close... if this is changed it may also throw off your TPS, so be aware...
Hope that helps!
Hi, my 3sgte stutters like mad :( Can I clean the IAC just by spraying Carb cleaner into throttle body without disassembling it? Thanks for the video Martin:)
peyeum Hi there,
You can try it, it might take a fair bit of fluid to flush it out well. Its possible though, that your stuttering may have nothing to do with the IACV, since the IACV mostly affects idle speed. Boost/vacuum leak, or refresh of plugs/cap/rotor may help you more in that area.
Hi will this hell sort my idling issue in my celica gt4? Im using a side feed intake manifold
It could... have you tested the function of the IACV? Start with just testing if it is operating correctly. What are the idling issues?
@@mkloppers yes it works when voltage is applied but wont drop below 1.3k high idle i followed your video and did the same but has increased higher 🤷♂️
@@Blackfracolin1 If the IACV is functioning properly when tested, and you even tried adjusting it towards fully closed, and it still idles high or even higher, you might have a vac leak that is allowing extra air into the intake manifold. Basically, air is bi-passing the IACV altogether, or finding a way to pass through it. Do a boost leak/vac test. Determine this first.
Then if not that, perhaps the throttle body plate is not closing fully, throttle idle/stop screw is shifting.
Do you have air conditioning?
@@mkloppers no ac it has been removed the vaccum line going to the throttle body when blocked idles around 0.5k when let loose gos back up to 1.3k.. even when warm does exactly the same a little higher on cold start but still drops down 1.3k rpm.. do u think blocking the vaccum line increase the throttle screw will fix this problem right now the screw is tightened all the way down? It has a standalone ecu fitted with a fmic all hoses seem fine checked the intercooler hoses and vaccum lines all seem fine and are new
which vacuum line is that, that alters the idle down to 500 rpm?
1:46
Hi Martin!
I have 4A-GZE with throttle body from MR-2 3S-GTE (55 mm dia instead of 45). When I start my engine it has no idle during approx. a minute or two. So I have to push the gas to make it work. Then I can release the accelerator and the engine is idling but with less revs (as well as I can guess - near 1000 rev/min, factory tacho from 4A-FE is not connected). Idling is not stable, it seems that there are some misfire. The bottom is rebuilt with new rings. I checked as well for air or vacuum leaks - everything seems to be fine (I sprayed sort of easy start liquid to all connections, when it gets to intake you can hear it at once by slower revs).
So what is your opinion, can it be the topic of your video causing lack of idling just after the engine start? Should I simply do same things that you showed on your video and it's gonna help?
Appreciate your help
Paul
A few things come to mind off the top of my head … the Throttle position sensor (TPS) I am not sure if it is interchangeable between the two ecu’s,
If the sensor is swapped out it needs to match the same “zero” signal (or be at the same angle and position)… if the sensors are still with their respective TB’s, then the 4a ecu is interpreting signals from the 3s sensor, so not sure if that is compatible that way either. That can cause the ecu to act uncharacteristically at idle.
Beyond that, yes, the IACV would be quite responsible for idle-up as you describe, and the airways would need to function from the TB to it etc.
The coolant hookups to the TB can be ignored and left unconnected if you don’t drive in cold winter.
So yes, the video info could apply in that regard.
Hope that helps!
@@mkloppers yeah, thank you so very much for your help, Martin!
As for the TPS - I forgot to mention that when I bought the throttle from 3S-GTE the TPS installed on it from the factory was not sending any signal, so I replaced it with TPS with same OEM part number as on 4A-GZE, with adjustment of its position of course. When my engine is warmed up, it is idling almost the way it should except some misfires. So can we put the finger of blame at the IACV?
@@paulgauthier2693 I would start there, the IACV if it were stuck shut, would explain the low or absent idle when cold, but not the misfires when warm. When it is warm/hot, the IACV would be closed anyway, and so the engine operation would be without it, and shouldn’t have any “misfires” due to the IACV.
@@mkloppers I really appreciate your help, Martin!
You said that IACV would be closed when the engine is hot. So is there one more valve that opens and provide fresh air as temp rises?
@@paulgauthier2693 no, the IACV should be the main controller of the difference between hot-cold engine idle, in combo with the ecu of course.
Other things do affect general idling and running. Have you done a boost leak test (vacuum test) for leaks? If un-metered air is sneaking in a different way it can cause erratic running at various RPM’s, and may cause the engine to be leaner than optimal at the start, especially cold start when you want the richest mix.