1UZ no idle, running very rich + missfire

[extractors]

Bearings are 6902V and 608V.

Just set the TPS per factory, .40mm closed then .65mm should be open between IDL and Earth. If you set it too tight it will be a bit touchy, and may go open circuit when engine hot etc.
Idle speed should be around 650 rpm when hot.

 

[Tremor]

Bearings are 6902V and 608V.

Just set the TPS per factory, .40mm closed then .65mm should be open between IDL and Earth. If you set it too tight it will be a bit touchy, and may go open circuit when engine hot etc.
Idle speed should be around 650 rpm when hot.

Ordered and ordered, Thanks again extractors for the insight. I have the "Non Rebuildable" unit so I was afraid of taking it apart but wow, it was completely seized.

New bearings coming in Monday as well as the rebuilt ecu this week so hopefully I will be on the path to smooth sailing ( and to the exhaust shop, I don't think the neighbors is too happy me pulling 3k RPM test runs on open headers)

 

[extractors]

Sounds like you are on track.

Make sure you update after new ecu.

 

[Tremor]

Sounds like you are on track.

Make sure you update after new ecu.

Thought I would drop the update I owed!

After installing the rebuilt ECU I am positive that was a huge portion of my issues. Engine starts up and runs great, I was able to even get a good pull down the road!
After sone I really only have one minor issue and of course, its related to idling.


On a cold start (50f) the engine is idling pretty high (1300 ish) and after awhile it dropped itself to about 1100 but seems once it gets warm it kind of "surge" for an idle.

It goes from roughly 900-1000 rpms up-down-up-down, roughly 1 second when its either up or down.
almost identical to this

I really tried to hunt but cannot find any real possible vacuum leaks. I unplugged the AFM, IACV, TPS and all had effects on how the engine ran but no real effect on the "hunt", again this is only warm.

I read in another thread that this is possible when the truck has no exhausts, do you know if there is any truth to this? as of now I am running straight out of the headers still but this seems way to drastic to be exhaust related.

This one is a thinker, otherwise trucks runs great under load, no complaints with the new ecu in place.

EDIT: After some closer investigating I can hear a "suck" extremely noticeably coming from the IACAV when it surges/stumbles. I unplug the IACV and there is absolutely zero effect on the idle and behaves the same way so maybe IACV is just junk? would that explain the corolation with it running like that hot?

 

[extractors]

Are you running o2 sensors ? if so unplug them. Just to eliminate them. They can cause idle issues when up to operating temp and the car will run fine without them.

Normally surging will be AFM related, but if it still does it when disconnected you have ruled that out.
Triple check every vacuum line ! PCV hoses etc.

Other than that wait til you get exhaust for more diagnosis. pretty hard to diagnose with a stupid loud exhaust.

 

[Tremor]

Are you running o2 sensors ? if so unplug them. Just to eliminate them. They can cause idle issues when up to operating temp and the car will run fine without them.

Normally surging will be AFM related, but if it still does it when disconnected you have ruled that out.
Triple check every vacuum line ! PCV hoses etc.

Other than that wait til you get exhaust for more diagnosis. pretty hard to diagnose with a stupid loud exhaust.

Hey extractors,

Thanks for the clues! Just to confirm do you mean primary or sub 02’s? currently I am running a new set of primary o2 sensors in the headers but I am not running any sub o2's or any EGR equipment. Do regular ones cause that issue? if so I will for sure unplug them tomorrow and test it out

I found a video displaying literally EXACTLY my symptoms with my surging just being a little quicker -

Essentially it starts as a normal idle, then warm starts to get around 1000-1500 rpm range then hot it starts going all over the place.


his ended up being an IACV

from what I have gathered from you and other forums my primary causes can be

● vacuum leak or misrouted vacuum line

● idle air control valve (IACV) is shot

● failing ECU capacitors

And on very very rare occurrences, TPS

To start, highly unlikely its caps, as it was just rebuilt

Next, vacuum leak or misrouted vacuum line. Possible but I think honestly unlikely. All of my EGR is completely deleted, every vacuum port not essential was capped and also clamped to avoid an air leak and doesn't have any fluctuation when cold which would be odd if it was a vac leak only present when warm. To be 100% sure I will pick up a can of flammable break clean spray it around the engine tomorrow and see if the idle raises.


Finally, IACV and TPS. I have the revised 94+ IACV "non rebuildable" which seem pretty fragile from everything I have read online. I have 2 units I have been testing.

Both units test good voltage, good resistance, good bearings, no damage or issues and yet one of them refuses to even idle on. This makes me think there is a way this is damaged/not working that is either not easily observable or not detectable from the outside. Judging from 2 videos with literal identical symptoms being the IACV I am going to take a bet both units I have are bad, and one is just a bit more bad.

One unit was a junkyard buy and the other from a reseller on eBay, I swapped the REAL bad one in and it dies immediately and wont hold an idle, I swap the other one in and it holds an idle but the associated surge stuff mentioned above


TPS tests fine with a light and behaves normally when everything is going fine so I really doubt that is it.


So far a f'd IACV (again) or a vac leak are my 2 main contenders, I ordered a tested and working or money back IACV from a very reputable seller so I will give that a shot next.

 

[extractors]

I have rebuilt quite a few of those IACV's, both for 1JZ and 1UZ. Very easy to do, you just need to drill and punch out the roll pin on the later model. Unless they are super clean they cause issues.

Sounds like IACV from what you have said. Won't be vacuum leak, disconnecting AFM will eliminate that as an issue.

Maybe TPS, but unlikely if IDL / E2 are closed at idle, have you confirmed that is still the case ?

But yes I meant the primary O2's, unlikely in your case, but do cause idle issues and unless they are genuine Bosch or Denso I don't trust them, aftermarket ones always fail prematurely, or simply aren't calibrated correctly.

 

[Tremor]

I have rebuilt quite a few of those IACV's, both for 1JZ and 1UZ. Very easy to do, you just need to drill and punch out the roll pin on the later model. Unless they are super clean they cause issues.

Sounds like IACV from what you have said. Won't be vacuum leak, disconnecting AFM will eliminate that as an issue.

Maybe TPS, but unlikely if IDL / E2 are closed at idle, have you confirmed that is still the case ?

But yes I meant the primary O2's, unlikely in your case, but do cause idle issues and unless they are genuine Bosch or Denso I don't trust them, aftermarket ones always fail prematurely, or simply aren't calibrated correctly.

The plot thickens,

I did indeed test unplugged my new denso o2's and sadly to no effect at all. I will test this theory again once I get it up to operating temp.


I came out today and we were back to absolutely no idle again, hmmm

I tried one main thing which in my opinion kinda sealed the deal, at a cold idle the IACV should be open to allow air past it to hold a good idle, Right? So theoretically if I pull this IACV it should be resetting after the vehicle is off so the iacv will be open.

well, I pulled it and it was 100% shut. hmmm that is odd. So I went ahead, manually unscrewed the iacv to open the valve up, re installed and it fired right up and idled.

So IACV if not the cause is for sure playing a huge role in this problem.

I took the IACV apart, cleaned spotlessly and insured my new bearings were working properly.

I know for a fact the IACV needs to reset properly for the vehicle to idle at cold correctly, so I went ahead and did glovermans test for this. I pulled the 6 pin connector off the IACV probed the 2 +bat center pins and sure enough, they instantly loose power.

damn ittttttttt

Not sure if this is all of it but this for sure a huge cause for idle issues especially for me the cold part

I have watched this video countless times but never put 2 and 2 together

According to kelvin, I wired something improperly. Per his video you can see the IACV light stay lit during the reset after the motor is off for just about 3 seonds. Mine it instantly goes off, meaning I have something running somewhere to the IACV wiring power that is straight ign on 12v rather then power from another intentionally delayed after key off source.

My thought is either that power related issue (though I have seen many of swaps with it wired this way) or b, its getting stuck when it tightens itself, going to get some more cleaning and testing and report back.


The IACV gets it power from the MREL wiring

MREL is supplied voltage from the efi relay, I currently have it going to (what I thought was correct) going to grn/blk EFI voltage which appears to be a constant 12v on or off which doesn't seem right as it should only be getting 12v if ign and bat are present, right?

 

[extractors]

When you shut the engine off does the IACV click a few times and perform its reset ?

Just unplug when the car is surging, idle should then stabilize and given RPM.

 

[Tremor]

When you shut the engine off does the IACV click a few times and perform its reset ?

Just unplug when the car is surging, idle should then stabilize and given RPM.

It does not, when the car is off there is no reset or anything after power is off.

When it's surging I did go ahead and plug off the plug and there was absolutely no difference. I finally of course after I finished found a perfect wiring tutorial guide swapping the exact same ecu into the exact same body harness and they have it wired extremely differently and I think I get what the main issue is.

The reason this problem presented the way it did for anyone reading this in the future is because other then being the wrong way to wire it up there is nothing really stopping at a base level from working and driving, but your start running into snags

Though everything runs fine with the way it is there is one main issue, the lexus ECU cannot control the Toyota EFI Relay and because of this key off = everything's off. This also easily checkable by running a test light in B in your diag box on the engine. There will be power on the B port for 3-ish seconds after. That is your sign your ECU is successfully able to control the IACV reset and MREL, instant power off= somethings fucked.

for anyone who finds this in the future after a long night again of analyzing...



I was initially using

il1 #2, #3 #12 #13 all going to toyota ih1 #14 (igsw)blk/rd
il1 #7 (Blk) going to toyota ih1 #22 (sta)black/w

e11 #4(blk/or) going to toyota ih1 #10 (mrel)blk/g
e11 #5(yel/rd) going to toyota ih1 #3 (cel)v
e11 #6(grn/rd) going to toyota ih1 #6 (FPR)blue
e11 #7(wht) going to toyota ih1 #7 (acmg)blu/ blk a/c not need to start
e11 #8(grn/blk) going to toyota ih1 #23 (fc)grn/y
e11 #19(grn/wht) going to toyota ih1 #5 (brake)grn/wht not need to start
e11 #26(blk/yel) going to toyota ih1 #16 (Batt)wht/red


And this was causing a myriad of issues and is not the right way to do this it seems, again mainly the fact the EFI Relay wasnt being controlled by the 1uz ECU

This is what I am switching it to

Toyota -- connector/pin/wire color - Lexus -- connector/pin/wire color - circuit description
----------------------------------------------------------------------------------------------------------------------------------------------------------
IH1/22/BLACK - EB2/1/BLACK - STARTER B+ CONTROL

----------------------------------------------------------------------------------------------------------------------------------------------------------

IH1/14/BLACK w/RED - IJ1/3,7/BLACKw/ORANGE - COILS/IGNITERS/INJECTORS

----------------------------------------------------------------------------------------------------------------------------------------------------------

IH1/16/WHITEw/RED - EB2/2,3/BLACKw/RED - EFI MAIN RELAY VOLTAGE (B+)

----------------------------------------------------------------------------------------------------------------------------------------------------------

IH1/10/BLACKw/GREEN - EB1/4/BLACKw/YELLOW - ECU B+ FROM EFI FUSE
---------------------------------------------------------------------------------------------------------------------------------------------------------
EB2/6/BLACKw/YELLOW - EB1/8/BLACKw/ORANGE - EFI RELAY CONTROL ON/OFF


I took care of most of these tonight but I will go ahead and finish up tomorrow and write back but based on my symptoms and testing it seems to likely be the case. This link is such a lifesaver

Engine harness connector ID's -- 1994 4Runner/1995 SC400

Engine harness connector ID's -- 1994 4Runner/1995 SC400

www.uzswap.com

 

[Tremor]

Welp,

Re wired and there is no change. ECU has EFI control and the IACV is still not resetting, B+ turns off as soon as the key is off

I pulled the IACV, paint pen'd where the IACV plunger is, ran the engine and pulled it off and it didnt even move.

Again, no notable codes.

Seems like the IACV is getting power but just not operating at all so the ECU tries to control the idle.

When I drove it out of the garage this morning, when cold started up and ran no problem. Once I got outside and it ran for awhile it start misfiring/stumbling and running like shit. Turned it off and then it would not idle again. Seems to me my IACV is both not moving and just not working. I would think even if its not resetting correctly due to a wiring problem it still should be able to control the IACV when running, I completely unplug it and there is 0 change while runing .

When you shut the engine off does the IACV click a few times and perform its reset ?

Just unplug when the car is surging, idle should then stabilize and given RPM.

I have power to the 2 middle pins, normal resistance on the sides, Im pretty much at a loss unless this IACV is just junk or I am missing something here

 

[extractors]

Just unplug IACV, you can always fix it slightly open for testing purposes.

You can do this simply for testing and manually setting the idle.

There's something else going on.

 

[Tremor]

Just unplug IACV, you can always fix it slightly open for testing purposes.

You can do this simply for testing and manually setting the idle.

There's something else going on.

Thanks for the link, that is quite the setup. man o man is that tempting. I suppose worse case I could rock that long term. I don't suppose there would be any negative long term effects, just a longer warm up in the winter right?

This is driving me up an absolute wall so I hope i can this sorted, I know this is almost turning into a build thread at this point.

Here are the important observations I have made today after working with the car


The important wires

BATT – E9-P33, The full time 12 battery voltage is good, getting 12v

IGSW – E9-P1 Key on voltage, getting 12v


MREL (aka my living hell wire) is supposed to supply 12 volts output on MREL ECU E9-P24, this 12 volts is used to switch the relay on. THIS is the wire that is responsible for the reset and is the pin that will stay on for 3-5 seconds post key off.

The MREL wire coming OUT of the ECU is outputting 4.42 volts

+B ECU E9-P31 +B1 ECU E9-P32 are the supplied voltage from the EFI relay, These are on the big red and black wire in the I plug responsible for powering both of these pins

for some ungodly reason +B ECU E9-P31 is getting 0 volts but +B1 ECU E9-P32 is getting 12 volts


(+ B) and (+B1) both get 12volts ONLY when the Main EFI Relay is switched.



2 main issues are one of the main ECU supplied voltage wires is not getting power, and the MREL wire is not producing the correct voltage suply. I will continue to troubleshoot

 

[Tremor]

Well, I have continued to narrow it down and I think I have a better understanding of what's going on now.


The reason it was not resetting is because the MREL wire that controls the reset should be tied to the EFI relay, the ECU controls this EFI relay on and off so it keeps the EFI Relay on when key is off for 3 seconds to allow the reset. In my first wiring arrangement the MREL was on switched ign only, but when it was switched the IACV would operate just fine.

I now have everything wired correctly, all ECU pins getting power, everything getting switch ign power correctly and the car runs, but my MREL wire is under powered??

It switches on when the EFI relay is on with ing+power but for some reason my ECU is only outputting 3.8 volts on the MREL wire, wtf?


getting pretty close to cutting my losses with the IACV and just run it in a fixed position unless anyone has any ideas on the idle front.

ALSO

pulled the IACV and discovered the disc cover that is at the base of plunger was cracked on the side, this allowed a lottt of freeplay with the bearing going up and down with the plunger, I wonder if it is related to the surging issue. Perhaps when the IACV had power and was attempting to wind out when the engine got warm the plunger had freeplay and caused random spurts of air in.

 

[extractors]

Its still shouldn't surge when the IACV is unplugged ?

You should be able to disable O2's, AFM, IACV and engine should idle fine if all other sensors are working, Cam, crank, tps, water temp sender etc. I still thing something else is going on, probably multiple issues.

Video the engine idling and post.

 

[Tremor]

Its still shouldn't surge when the IACV is unplugged ?

You should be able to disable O2's, AFM, IACV and engine should idle fine if all other sensors are working, Cam, crank, tps, water temp sender etc. I still thing something else is going on, probably multiple issues.

Video the engine idling and post.

Hey Extractors thank you again as always for your help,

Something is/was causing only the 4.8 volt output on the MREL pin from the ECU the grounds are right, the relay is right but for whatever reason 4.8, whatever. I hardwired the MREL wire to get a ign switched 12v. My IACV has started to work again and definitely corrected the other issues.


Here is the requested video of the issue I am currently working with. This is what it does now instead of surge or its likely it was doing both.

The engine starts up high rpms for 1 seconds, drops to 1100 and idles like a dream at first start. Then, as the engine starts to get warm it begins misfiring more and more and then when warm it runs as shown in the video.

I unplugged

IACV
TPS
AFM
O2's (new OEM denso's)

and no change. I am going to check the temp sensors first then probe the cam and the crank as well.

Im just thinking out loud but the thing that make the most sense seem like maybe the temp sensor, its just odd the other components that could fail (crank sensor, cam sensors etc) wouldn't show symptoms at cold

 

[Tremor]

ECT Temp sensor tested 1.205 volts at 646 ohms and raises as temp drops as it should.


Coil 1 test 13.95 kon primary and secondary
Coil 2 tested 12.7 k on primary and secondary

Crank sensor tested 1.22K

cam sensor 1 was at 1.208 k
cam sensor 2 was at 1.95 k

 

[extractors]

Cam sensor 2 a bit high, but then they should run on one only. can unplug it and shouldn't have any effect ?

Mine have been around 1K cold around 1.3 k hot.

What happens when you crack the throttle ?

Check plugs, sounds like its running lean to me ? You sure you have plenty of fuel flow ? Again those chinese injectors don't have me excited at all.

 

[Tremor]

Cam sensor 2 a bit high, but then they should run on one only. can unplug it and shouldn't have any effect ?

Mine have been around 1K cold around 1.3 k hot.

What happens when you crack the throttle ?

Check plugs, sounds like its running lean to me ? You sure you have plenty of fuel flow ? Again those chinese injectors don't have me excited at all.

Well eventful few days.

To avoid any confusion for myself going forward I have built an independent harness for this harness with tried and true schematics from Kelvin at cartuneNZ

I also found 2 key things.

1.) The way it was wired as advised to by the toyota forums swap section almost everything was getting underpowered, usually around 11.4.11.75 volts, fuel pump, inj circuit everything. I am hoping that what was causing most of the lean conditions, misfires, etc.

2.) The MREL is EXTREMELY crucial to have a 12v output in these engine setups any way you do them. The EFI Relay absolutely relies on this and without it very very weird sh*t will happen. The ECU receives 4 things to do this IGSW,B+,B1+ and ground. If one of these is not present, you will not get a 12v output on that wire.

Well, all of the above mentioned wires were present, and I was getting a unchanging 7.8 volt output from the ECU....... hmmm and when I tested with another ECU, I got the correct 12v output from MREL. So, the rebuild yet again, was bullshit and not done correctly. Luckily this order is recent and I have already messaged the seller.

For now I have ran separate IGSW power to the MREL wire to supplement this output. As of now everything now is getting the correct voltage. I will wait to confirm anything is fixed until I run the engine tomorrow.

 

[Tremor]

Welp,

It still 100% has a faulty ECU.

Had the truck wired up and started running ok, same issue but with more surging and less misfiring drove it out of the garage. very weird.


Turned it off and turned it back on and all the sudden started getting weird codes:

Ign bank 1, coolant temp sensor, etc. Stuff that was working fine 20 mins ago plus the MREL wire not outputting the correct voltage and not staying on when key is off, these are the same fucking symptoms it had BEFORE I sent it and paid 230$ the second time to have this "re built" These people seem more reputable and immediately offered to re test and paid the shipping so I can complain too much. I really would like to have this truck run before snow is flying.