1jz vvti wont idle mx73

[sundee86]

i've got my jzx73 conversion all wired and running etc, here is a pic

6C00E4D2_zps25f612bb.jpg

But it wont start with the IACV connected without a foot on the throttle.

disconnecting the IACV connector lets the motor start un assisted but it idles at approx 1200rpm when warm.

What ive done to diagnose the issue:

- removed and cleaned IACV
- checked 12v to center pins of IACV connector (12v present)
- applied 12v to center pins of IACV and earthing existing pins, valve stays shut (i was under the impression the ECU should open the IACV after shutdown in prep for the restart?)
- checked ECU for dry joints or blown caps
- Ran codes, got code 39 (vvti system error) - i know the VVTI solenoid is faulty, waiting for another solenoid.


So ATM i need to leave it disconnected for the engine to start and idle.


i have noted the following:

- wont start with IACV connected.
- Disconnect IACV and engine starts unassisted but has hi idle approx. 1200rpm
- re connected IACV while engine was running, Idle came down to around 700 rpm (tach is not working so just by ear - normal idle speed)
- did the above again, after reconnecting IACV there was no idle change, this is what it continues to do.

any other suggestions before i change the valve?

thanks in advance

[sundee86]

going to test and reset the TPS and throttle stop today, see if it makes any difference.

[George]

I don't remember if it's stepmotor or servo controlled, check your repair manual. Apparently a stepmotor controlled IACV won't move unless you supply the proper pulses to it.

Also note that 1JZ IACV's are not uncommon to get stuck. Coil windings are prone to failure,too, so be sure to check them with an ohm meter (whether they're broke or not).

[sundee86]

wish i could get my hands on a repair manual that i could read (aka english)

[George]

there's no such for a JZX100 afaik
maybe a 70/80 n/a Supra manual would be of any help tjough

[dumbass]

u might have wired it wrong
did u use the efi relay from the mx73
I think the efi relay on the mx73 is controlled by ignition
where as the efi relay on 1j should be control by ecu using mrel wire

I know if this is not wired correctly then the ecu wont reset idle motor each time u turn engine off
its common problem

[George]

let's start with knowing if it's n/a or turbo 1jz
for example, pre-1999 n/a 1jz ECU has no MREL output

[Daddio]

Sounds more like a TPS issue? The IACV should open fully when IGN is turned off (and I'm pretty sure it is powered by the constant live feed to the ECU and not the MREL live input) but the IACV wont adjust itself unless it gets a throttle closed signal from the TPS. You should be able to hear/feel the stepper motor opening fully on IGN off.
Suggest check your TPS is functioning correctly and adjusted correctly to give a throttle closed signal.
Also, as mentioned, a good clean of the IAVC never hurts as they are prone to sticking.
Testing the stepper motor coils is pretty easy (check resistance between each of the 4 outer pins and the two center pins on the plug)

[dumbass]

hey George I doubt u will ever find an early 1j NA with no mrel wire here in Australia

if the mrel wire isn't hooked up correctly it can cause all sorts if silly problems

u can test idle motor by giving centre pins 12v and the very quickly touch each other pin one at a time
no real order which one to touch but u will feel the motor twitch each time
but it is common for idle motors on 1j and 1uzs to stick unfortunately good second hands ones are hard to find

[George]

dumbass in my place, I saw them here and there just a couple years ago, then looks like the importers instantly switched to the newer engines (those with 5-connector ECU). Anyway, sundee86 should have mentioned the exact engine model in his first post for clarity

[sundee86]

Sorry guys, engine is 1jzgte vvti from jzx100 (4 plug ecu)

I have wired mrel output from the ecu (pin 2/16p) to the mx73 mrel, PIN # 2 from memory.

I'm just waiting for the rain to stop bashing down on my shed so I can re test the iacv, can't hear squat ATM!

I've got another iacv that I have tested and I can hear and feel it do it's thing, just need to re test the one on the motor.

[BLK_20v]

Dumbass how do u draw that conclusion regarding the iscv wiring...



To me it gets ign power from the efi relay which is opened by the mrelay on the ecu.

[dumbass]

Hey George. Yer australai gets all the crap motors

Blk 20v u need to know why the toyota ecu controls the efi relay
Mrel holds the efi relay on for a second or two once u switch car off
In those two seconds a lot of things happen and if u search there have been
Afew guys on here having all different issues and sometimes it has been due to mrel
Not wired correctly many years ago
But he has wired it correctly so it's probably not that
But when diagnosing u have to learn how to check everything quickly otherwise customer ends up with a thousand dollar bill
So u slowly learn what can cause these issues and it all comes from decades of wiring

There is usually 4 big issues with an idle motor playing up when people wire toyota engines

1. No power to idle motor centre pins
2. Stuck idle motor. Is probably the main cause especially if its doesn't even budge
3. Mrel not wired right means idle motor won't reset after each engine shut down
4. Idle switch not set right. But never really seen this much

I would block off pipe feeding idle motor and see if it acts exactly the same
If it does then its prob seized idle motor

If idle motor does adjust sometimes then it might be wiring or dirty idle motor

[sundee86]

Today I got another iacv, tested it and the one in the car.

The iacv I got my hands on was open.
The iacv I pulled out off my 1j was closed.

I tested both by putting 12v to the center pins and earthlings the other 4.
The replacemt iacv seemed to react more when earthing the pins, ie it seemed healthier.

I put the replacement in, and now it won't even idle with the iacv plug disconnected .
With the original iacv it would idle up to 1200 rpm ish.

I pulled the throttle body to replace the ocv, that fault code has gone now.
Ps - iacv from 3sge beams fits, just need to re bend the bracket.
Throttle body got a good clean while it was out.

I can't seem to find a definite test procedure and figures for the tps.
It's not the same as 1j non vvti because the primary tps on the vvti jzx100 JZ motor is not adjustable.

Anyway I need to re test it, my figures were differnt from the ones I was comparing to.
If anyone has the correct test/adjustment procedure that would be awesome, there are ones out there but who knows if they are right because they are all different.

All I could do was wind in the throttle stop to keep it running...

[sundee86]

Oh and just to add to it all now, it's throwing code 78 on the cel. Amazing!
Thanks for your help fellas, appreciate it.
Just wanna get this thing completely sorted