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4K EFI Test Rig - IAC Valve


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Been a few years, since I built this test rig, but after getting all the trigger sensors alright on my 5K test rig, with a Speeduino ECU, I've moved the COPs & trigger disk/wheel over onto a 4K with a 7K EFI setup.



Only got the fuel tank with inboard submergible pump to sort out, & then I'm almost there.

The trouble I'm having is  trying to work out how the Idle Air Control Valve (IACV)  is powered/controlled.




The  IACV has the coolant plumbing, which appeares to heat up some sort of  sealed wax of the like. (no removable plate with bi-metal spring like some IACVs I've seen on the net)


The one I've got is stuffed, as the spindle turns easily. The electrical drive at the other end, has a 3 pin plug, which  I believe needs a switched  +12  or +8V volt source on the centre pin, & a high frequency  earthed pulse train on the two outer pins. 

I've ordered a new IAC Valve & actuator, which in a DENSO model 22270-06020. 

As I will be controlling this via an aftermarket ECU, I need to know what the two control signals look like in terms of voltage, frequency, & PWM (pulse width modulation) requirements.

Has anyone on here had any experience with this particular IACV ?  I've spent 2 nights on the Net, & can't find anything specific, about it's driving signals requirements.

These were used on 7K-E engines, on Toyota Lite Ace vans & the like.

P.S.  Anyone got a 7K-E Toyota Workshop manual, in pdf format or hard cover, they want to sell or loan ?  None of the pdf links on the web seem to work.

Cheers  Banjo

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Would the electrical side to be a sensor, rather than an activator?

The 4AGE has the waxstat that opens and closes an air valve depending on temp, and the ECU must read the oxy sensor in the exhaust to see how much air has gone in. So cold idle has more air & fuel, reducing as the motor warms and the waxstat closes.

What if yours has a waxstat to regulate air volume and the rotary windings that look like a TPS are telling the ECU how much air is being let in?

If the rotary part turned the waxstat part you wouldn't need a wax cylinder, the ECU would control the air volume like a stepper motor.

There's too much I don't know!  I'm about to learn another lot as the Sprinter came back looking like this after Steve drove through a particularly deep stream at the Batemans Bay rally.


While we could spend a lot of money rebuilding the 4AGE, he reckons just move onto the 3SGE that is sitting there awaiting the Orange Cake.  That makes sense, but it will take longer to do and I remember the electrics of fitting an ECU to The Girls KE70 were quite taxing...  Looks like I'll have to step up a notch in Toyota electrics, its time to learn laptop tuning & troubleshooting..

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The U-Tube video clip in my previous post, describes the general operation of the IAC / IACV / ISC which are terms that are used for this device.

IAC = Idle Air Controller  IACV = Idle air Control Valve    ISC = Idle Speed Controller

The guy in the video is a tech teacher in Kiwi Land, & is a good communicator.

He obviosly did a lot of reseach for the presentation, which He mentions, was hard to find.  I did actually find a place where I could download the 7K-E factory manual last night. 50Mb & 264 pages.  However, still doesn't provide the specifics of what I need to know about the electrical controlling of the IAC valve, in terms of frequency, & PWM requirements.  The particular Toyota IAC valve he was using, did infact have a small adjustment of the bi-metal coil, which is totally under the control of the coolant temperature.  As the 7K-E throttle body, has an end stop adjustment, you could use the IAC valve, without the  ECU input, & just use it for increasing the idle speed on a cold start.  However, the possibilities once the engine is up to temperature, & running; especially in motor sport applications, & traction control, are awesome. 

Once I receive the new IAC valve & actuator assembly, I bought on-line, I can play with the electrical ECU controlled actuator, & work out how to drive it. It is done by two electrically induced magnetic fields in balance. Moving the actuator, is achieved by increaing one magnetic field, & reducing the other.  I have no intention of using an olde

7K-E ECU, (even if you could get hold of one), to control & drive this arrangement.

All good fun !


Ouche !  Couple of tubes of Araldite or Gorrilla Glue should fix that !

Cheers Banjo

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Ah, I see, it uses an old bimetallic mechanical system plus a computer controlled system as well.  I found the other sort, the PWM linear valve, explained here-


That runs a 2-pin system so the Haltech can control one of those. I might leave the waxstat in The Girls KE70 as it gives a good cold idle at -2deg, and see if a PWM can control the warm idle.  The Evo3 rally car runs a Bosch unit like that, only they're $330, while a nasty copy for Audi/VW on Aliexpress is $20 !!.

Anyway... next year's problem..  by then you will have your 3-wire sorted out and we will both know more.


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That description is as good a simple description, that I've seen.  It doesn't mention coolant temperature control, using either a wax chamber, or bi-metalic spring; but could also use that same function; as the ECU measures & monitors coolant temperature.  The beauty of the DENSO one I'm using, is if the signal from the ECU fails for any reason, you still have an adjustment on the trottle body; to crack open the throttle butterfly, to supplement the initial bypass valve opening, so that the engine will idle initially, with the temperature at cold start up.

I think is called the KISS principle.  Keep It Super Simple.

The only thing I would question in the description, in your link, is the statement . . .  "This makes the plunger inside move forward and backwards very quickly."  In practice, the "plunger" maintains a relatively stationary position for a partular mark/space (On/Off) ratio.  If the plunger was flying backwards & forwards very fast all the time, it would werar out in no time.  In practice, the electrical signal from the ECU, changes very fast, but magnetic forces & the inertia of the plunger magnet don't; so it tends to find a steady spot, somewhere inbetween full open, & fully closed, based on the electrical indiced magnetic force, applied to it.  That is why the frequency of 100-300Hz is chosen, so that it's time constant, is faster than that of magnetic field.

This afternoon, I've been looking at where I will run the coolant hoses to & from, the IAC valve.

The plate on the back of the head would be a good  starting point.  That's where there is  take-off point, for the heater. A good return point, would be the thermostat housing on the 4K, which has one large entry hole. However, that position, is on the backside of the thermostat, so maybe, on startup, when the engine is cold, & the thermostat is still closed, that  would not create much flow, in the coolant line to the IAC valve. There is a small pipe on the water pump (inlet side), so that may be a better spot. I have actually come across a top spout & hose connection point housing, which covers the thermostat, which has a flat on the top, where a return line could be connected to. 


However, that results in the return water going through the radiator, when you really want the engine coolant to warm up as quickly as possible.  "Proof will be in the pudding", & I can always measure warm up time, & change connection points for the best result.

Cheers Banjo


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Well, you wouldn't need much water flow when the t'stat is closed, its all still under cold start conditions. When its at 60deg for 20seconds & climbing, would your idle be too fast??  Then it hits 70+deg & the t'stat stats to open and you get warm water through the waxstat.

A bigger factor would be the pressure ratio in the line due to the pump, you'd need to come out of the back of the head and feed into negative pressure side of the pump where the lower rad hose goes in.  The t'stat housing will be at positive pressure, the same as the head.  I suppose its the same as the heater hoses, anywhere that give circulation or the waxstat will lag warmup by a few minutes.


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In Brisbane, with only a few days of winter left; yesterday was a beautiful day to spend in the "the shed", as my better half calls it.


you'd need to come out of the back of the head and feed into negative pressure side of the pump where the lower rad hose goes in.  

Before I'd even read your post, Keith, that is exactly the conclusion I came to, & what I did.

There are lots of reasons why it is good doing this type of mods to the engine "out of the vehicle". Access is great, when it is on a test stand.

The plate on the back of the head, can be a pain. The four small 6mm bolts holding the plate on, often become rusted & break off. When you get the plate off, the water jacket, in that area, is often full of corrosion & build up.

I was very lucky, in that all four (4) bolts came out easily, & when the water jacket was exposed; it was as "clean as a whistle".


I had never had this 4K engine apart, so it was obvious; a previous owner had; so I was lucky.  Even the back of the plate, where it is exposed to the water jacket, is often pitted & thin; but this one had little pitting, with plenty of metal thickess left, to fit a hose fitting.


I found a hose adaptor fitting in my box of junk, the same as the hose fitting on the IAC valve, so I could simply run the same hose, from one to the other.


The return run from the IAC valve, to the water pump inlet, is quite short.  However, the spare inlet point on the water pump; adjacent to the radiator bottom hose connection, is far to large, for this particular modification.  I eventually, cut the casting spout off altogether, & because there is a lot of metal in that area, I drilled it out & threaded it; & again fitted a brass hose adaptor, for the 5/16" hose I intend to use.



It did involve removing the water pump, so I could hold it in a vice, on the bench, but I didn't have to remove the radiator, to get at it, which is something, that would be difficult, if the engine was in the car.  So off to get some hose today, & that ticks that job off.  Will have to await, until the engine is running, to see if the IAC valve action, performs, as anticipated.

On the front end of the fuel rail, on the 7K-EFI setup, there is a device, that I'm assuming, is a fuel pressure regulator, with a threaded hole, which I assume is the return fuel line to the fuel tank.


There is no obvious adjustment possible for the regulator, so maybe it is non adjustable.  I might just plug it off, & fit an external regulator.  Someone on here, who is more familiar with the 7K-EFI setup, might be able to put me straight there.

I have already fitted my trigger wheel, using a 150mm dia. aluminium disk, with small rare earth magnets embeded, which worked so well on the 5K engine. 



All I need now is to produce a cam position signal; so that is the next job.

Cheers Banjo






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That sounds like plumbing that will work..  mind you, we will want it flow checked to confirm!

The 4AGE runs a fuel pressure regulator on the return line, set to only 45psi. The diaphragm line goes to the inlet manifold so when you boot it and the vacuum drops to nothing you get a quick enrichment as it closes the return line and puts the pressure up, an electronic pump jet!

...and now you've done away with the distributor you'll have to make your own cam sensor!  The  4AGE uses the dizzy readings to act as crank/cam sensor. What did the 7K ECU use originally?  Do you put the original dizzy shaft back in with one magnet set to #1 firing?  I suppose that depends on what the ECU needs to read..

Have you compared the 7K ECU pinouts to the 4AGE's?  Are they the same vintage, the early 80's? Toyota tended to do the minimal changes to stuff between cars then. You might be able to swap a couple of systems over, like that fuel reg and the dizzy setup.

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The 4AGE runs a fuel pressure regulator on the return line, set to only 45psi. The diaphragm line goes to the inlet manifold so when you boot it and the vacuum drops to nothing you get a quick enrichment as it closes the return line and puts the pressure up, an electronic pump jet!

I think the 7K EFI setup does the same thing. when I take a close look at this "fuel pressure regulator", mounted on the end of the fuel rail, it does have a small push on rubber hose fitting, which goes back to a point on the inlet plenum.

I have got hold of a Toyota 7K workshop manual, & the specs say the fuel pressure regulator operates in the range around 38 PSI.  That all makes senso now.  I'm going to fit a fuel pressure guage on the fuel line into the fuel rail, at the opposite end, so I will be able to easily check that the regulator is working or not, by applying some vaccum, to the little hose to the regulator.

I've never actually seen a 7K engine complete, in the flesh, so maybe someone on here, that has a 7K-EFI could comment.

Not quite sure how the 7K-EFI ECU gets it's cam position information.  The 7K used a standard sort of distributor, so the actual HV spark to the spark plugs was distributed in the usual way.  The manual talks about a NE signal.


Not sure how four points on the crankcase let you know where the camshalf is positioned.  Although called a crankshaft postion sensor, it is actually sited in the distribuor itself. 4 pulses in the distributor, would produce 4 pulses for every 2 crankshaft revolutions, which is a full cycle.  The 7K EFI has 4 off injectors, unlike I belief, the 4K-EFI, which used a single injector, & sort of batch fired.

There are a couple of ways I can produce a cam position senor output.  The 5K I did it on, was off the camshaft chain sprocket, which worked well, but it requires the timing chain cover to be removed. I then tried using the lobe on the cam shaft, for the fuel pump, (which I  am not using), as a camshaft position pulse generator. It worked, but was a bit borderline, so I diced that idea.  The dizzy shaft is the best spot, as even if you abandon the dizzy altogether, you still need the shaft to turn the oil pump. On the 5K I just made up a dear little dummy shaft, by cutting one off, below the distributor, & putting a little cover over it, to retain the oil sealing.



I may do exactly what you suggest, by putting a single rare earth magnet off the dummy shaft, & pick it up with a sensor.

On my KE30, I have been running a 3K dizzy for years, very reliably, with a Hall Effect elctroniic sensor & ignitor. They simple replace the points, in a standard dizzy. I just loaded the ignitor output with a 100 ohm resistor, & used that single to feed to the ECU.


I could easily do that, & only leave one lobe on the "rotor" piece, so it generated one pulse per dizzy revolution.

Lots of possibilities there, so will have a play later on today, as I already have a "gutted" 3K dizzy here on the bench.  I like the 3K dissy, as they were the smallest of all the dizzies, fitted to K Series engines.



Cheers Banjo


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OK, not the same. The 4AGE has three wires to the dizzy, Ne, G and G-  

Inside the 4AGE dizzy are two setups, both busily counting teeth. Only 4 on top, like you say, but 24 on the bottom. Other 4AGEs had 4 on the bottom & one on the top.


So you're not going to drop a 4AGE one in there...

4AGE bigport dizzy.jpg

4AGE ign wiring.jpg

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Thanks for that photo of the innards of the 4AGE dizzy.  I must admit, I've not seen a 4AGE dizzy previously.  The 4  tooth, top trigger wheel is like the conventional points, & fires the coil in the normal way, & distributes it to the spark plug via the rotor.

The bottom 24 tooth multi-tooth wheel, is I presume representing the crankshaft position.  I notice a missing tooth; but maybe there are two missing teeth, on opposite sides of the wheel, as the dizzy does one revolution, for every two of the crankshaft.  Some Nissan dizzies had a similar arrangement, that used punched S.S. disks with light sensors either side of the disk.  There were two circles of punched holes.  Again one was for the cam/dizzy position, & the other for the crankshaft.  

Few, if any manufacturers use that method now. The most accurate way, to measure both engine RPM, & crankshaft position, is off the crankshaft itself. The problem with trying to measure crankshaft position with the dizzy; is that inbetween the crank & the dizzy, is either a chain or a belt, & then there is the gear off the camshaft, to dive the dizzy.  All opportunities to introduce angular errors. (We all know, how much slop you can get in a K series camshaft sprocket chain).


My first experiments started measuring the flywheel ring gear, used by the starter.  That worked well, but was difficult area to get at, in most vehicles. I believe a few European cars used the ring gear teeth, years ago.  Probably the French, as they are always a bit different.

The camshaft position sensor, only provides one (1) pulse per two (2) revolutions, of the crankshaft.  It doesn't worry about a bit of slop in a chain or belt, etc, as it's only purpose in life, is to let the EMS/ECU know that the next cyclinder to reach TDC, is going to be cylinder no: 1.  ECUs are programmed with the firing order, so once the cam position, advises which cylinder is next to fire, the ECU can work out the firing order from that point on.

So tonight I'll be cutting a 3k dizzy case in half, & see if I can't attach a rare earth magnet to the "locked up" shaft, & put a Hall Effect snsor through the side of the case.

Mind you; we don't want anythingm  like this "over the top'"  type crankshaft trigger wheel, on a Rolla. 



Cheers Banjo



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On 8/24/2022 at 8:21 PM, Banjo said:


P.S.  Anyone got a 7K-E Toyota Workshop manual, in pdf format or hard cover, they want to sell or loan ?  None of the pdf links on the web seem to work.

Cheers  Banjo

Try here ~ https://drive.google.com/file/d/14P1j8GZ7udpCkTSQ5bCyOs3EysRu0r26/view?usp=sharing


Edited by frosty
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Thanks Frosty !  Got it.  I actually had that one, which I had acquired off the internet some time ago, but it had been laboriously scanned by hand, & the diagrams were very unclear. The one you posted, is much, much better.  Thanks again.

Cheers Banjo

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Cam Position Sensor MkII for a K Series Engine:  So ! gutted a 3K dizzy completely, so that it was just a shell.  No vacuum function, or bob weights etc. All gone.

Cut the centre shaft right down, & pressed a small aluminium block onto the centre shaft top, so I could drill a 3mm hole horizontally to mount a tiny 3mm dia. rare earth magnet. (Glued & pressed in to a slightly undersized hole)   Cut the alloy case of the dissy, in half horizontally, to reduce it's size.

Drilled a hole in the side of the case, to line up with said rare earth magnet, & there you have it. The Hall effect device, will run on any voltage between 6-36V dc.  It has a little LED on the rear end of it, so it is easy to check it is working.  The barrel of the Hall Effect device is threaded, so it is very easy to set the gap between magnet face & Hall Effect sensor, which is not critical.  The pulse is a good width, of about 20 deg. of the rotation of the distributor, which means it is on for about 5.5% of each rotation.






Put a lid on it, which I'll add a couple of clips on the dizzy casing, to hold it in place. Will probalbly use the clips that held the dizzy cap on originally.


Yes, it does say "ORANGE" on the lid, as I raided my wife's jam jar cupboard, whilst she was out shopping, & found a lid exactly the right diameter.


About 2 hours work, & just a sensor that comes in under $ 10.  How simple is that !

Cheers Banjo

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