1UZ overheats, no power, no codes..

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a7mgte

New Member
Messages
22
Location
Morro Bay, CA
The engine is a 1UZ in an 86 4Runner, and has 38,000 miles on it, from what I was told was a 93 SC400. (Ebay motor) It arrived perfectly clean and in perfect shape, so I don't doubt the mileage. I'm running a 91 LS ECU (I think) though, could they be different?

Currently there are no engine codes at all. (I just solved the EGR code that was bugging me forever.)

The engine is putting out about 100hp or less maybe. It loses to my friends 4Runner that has a stock 22RE on 33's. ...and it runs HOT. Despite having an aftermarket 3 core aluminum radiator and 16" 2300 CFM puller fan with a shroud.

It doesn't consume coolant or oil, although does seem to blow a little steam while at idle, it doesn't smell the least bit sweet like I would expect if it were burning coolant. It starts perfect, idles smooth, and the power band seems consistent over the RPM range, with the exception of the POWER part of that statement.

I've checked about everthing that I can think of short of doing a compression test. The TPS and AFM checked out fine as outlined HERE. When I installed the motor I did have to wire in the rear 02 sensors, but that was no big deal, and I also had to wire in the stepper motor for the EGR to get rid of the check engine light, as my ECU expected to see that motor. I've pulled the exhaust off thinking that maybe I had a clogged cats or something. I just verified the timing belt didn't jump a tooth, and put new plugs, cap and rotor on it while I had it apart. The plugs were a little dark, and smelled so rich you'd think they belong in a lawnmower though.

The motor is practically brand new, not a hose or wire on that thing is even the slightest bit brittle. I can't for the life of me figure out what must be going on. Could the primary 02 sensors get bad enough to make it behave like this and still not throw a code? ...is there a good way to test them before shelling out a couple hundred bucks for new ones?

With all of that said the truck absolutely will not provide 1st gear under power, no matter what...only when in manual low and I let off the gas does it downshift. As though first and second gear are reversed. I don't know if this could be relevant, but you never know. I have given up on trying to get it to shift properly though, and will be installing paddle shifters in the the steering wheel soon to skip the ECU's control of the tranny altogether.
 

gloverman

Well-Known Member
Messages
2,968
Location
Hamilton. New Zealand
Sounds like you need to recheck your wiring. Whats the number and pin configuration from the ECU. Normally these kinds of issues are all related.

I had to fix a vehicle which lacked power a while back , also got hot. Didnt notice a trans issue. Customer had recently purchased it for about a 1/4 of the cost of building it. Put it onto the dyno and it made 60rwkw. It was actually retarding the timing to ATDC when reved hard. It had new plugs , leads , caps and rotors. I could see signs of people working everywhere on it. Took me a while to find the one signal that had been wired wrong but I did find it. Doubled the power and sorted the overheating.

Check it one wire at a time , comparing signals with what should be there. I did have most parts to swap over which made isolating it to a wiring issue easier.

Cheers
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
The ECU has the three 40 pin connectors. I guess you could say the larger one has 80 pins.

The loom for this engine is all in tact from the factory. Nothing was changed aside from the few wires for power and the gauges.

I have gone over all the power connections to the ECU several times now, and can't find anything wrong. I'm getting about to the point now that I'm starting to suspect that it's just not getting enough amperage to the ECU from whatever source I've given it, or that there may be a connectivity problem between the ECU connector and the computer itself.

Primary power for the system was wired into the loom from the engine harness using a pair of 35a relays in the engine compartment. I don't see how the ECU couldn't be getting enough power from them, but I think I may move the relay in by the ECU itself and power it from that side of the harness first.

I didn't use the ECU's "STA" wire to the starter relay, but opted for the one that was already in place in the truck.

I also haven't hooked up the STP wire to tell the ECU when I'm stepping on the brakes. I wonder if that pin could be floating...nah, it's not like there is a pull down resister in the brake switch under the dash?

The "ECT" circuit was left open, but I have wired it closed to the PWR position. This didn't seem to make any difference at all.

The "OD" switch was never wired up, so it should be ON, since power to that pin should turn off overdrive if I'm seeing the schematic right.

Off hand that's all that I can think of that is different than what it should be. I wouldn't think that any of them would cause anywhere near this kinda trouble.
 

gloverman

Well-Known Member
Messages
2,968
Location
Hamilton. New Zealand
STA is an input and should be wired correctly. Same with the OD and STP. It needs STP to select first gear when you come to a stop. Otherwise it will hang in second most of the time - sound familar?? OD needs to be wired correctly to allow flash codes from the ECU. Did you wire NSW? All the gear inputs? You actually need to wire the ECU correctly to expect it to work correctly. Does the ECU have a check light when you turn the key on?
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
I do have a check engine light and fought with code 71 for some time before figuring out that the ECU wanted the stepper motor for the EGR instead of the VSV controlled one that was on my motor.

I'll have to look at STA again a little closer tomorrow. I thought this was just to control the starter relay, rather than to tell the ECU that the engine is running.

STP does make some sense, but it's just an open / closed switched input. From what I've read about it, it does tell the ECU that you are stepping on the brakes, but that it was mostly just used to unlock the torque converter so the engine doesn't bog down too much or stall should it somehow stay locked up at a stop. Even with it wired up, it's condition would still be low (0v) when I accelerate down a residential street causing a kickdown to first. I'll wire it tomorrow anyhow...

I didn't wire up OD yet, because I don't really ever plan on turning it off as I don't ever see myself towing much with my rock crawler...and god knows that slowing this thing down will probably never be a problem the engine can help with.

I did hot wire the OD pin on the computer to an LED to try and pull any transmission codes. That turned out to be interesting since it produces an inverted signal to what I was expecting. So I had to count the number of times it was off rather than on. When I did this though I realized it I hadn't cleared the codes from a test drive I did with the tranny unplugged, so I disregarded the codes and reset the ECU agian. No codes anymore. I was really hoping to get one too. I do plan on wiring this up properly though, if only so that I'll know if there is a fault in the tranny and it makes pulling the codes far easier than the LED method I did earlier today.

I'm pretty sure that I did wire up NSW, but I'm gonna have to get back out and check it again. The truck has been sitting since last summer pretty much, and I'm just getting back out to deal with these issues, so my memory of every wire isn't what it was 8 months ago. :-/
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
Kick down switch also helps getting first on hard acceleration from low speeds.

I keep thinking about this switch, but haven't figured out a good way to implement it in my truck. I didn't even think to pull it out of the donor car than gave me my tranny, since I don't recall anyone else having put the thing in when doing their swaps.

Since for the most part people tend to be overly intimidated by the power that this engine produces in their trucks, I haven't really thought that it's something that would be needed.

I think that putting it under the gas pedal would be a bit too much work for me, and I'd be affraid of breaking the thing due to my lead foot, I was thinking that I may add it to the steering wheel as a "passing" button of sorts. :D
 

rma

New Member
Messages
100
Location
san jose ,ca USA
you say your using a sc engine and harness but a ls ecu...the connectors and ecus are different....how did you connect the sc harness to the ls ecu,did you cut off the sc connectors and splice in the ls ones maybe that's where the probkem is.
as for the kick down using the Ls kick down at the pedal is pretty easy to do
in our runners.i also used a micro switch at the throttle body on one swap.good luck man.
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
STA is an input and should be wired correctly. Same with the OD and STP. It needs STP to select first gear when you come to a stop. Otherwise it will hang in second most of the time - sound familar?? OD needs to be wired correctly to allow flash codes from the ECU. Did you wire NSW? All the gear inputs? You actually need to wire the ECU correctly to expect it to work correctly. Does the ECU have a check light when you turn the key on?
I'm out looking at the truck right now, and checked NSW. I have it wired so that it receives power in the "start" position only. To me this makes sense, as it makes the ECU think that it's in park or neutral allowing the engine to start. I don't know what other use for this wire there is other than that. I don't have my shift lever wired up in the cab, but was thinking that I could tie it into the P and/or N on the shift pattern switch on the tranny pretty easy since all that wiring is already in place. That way it's getting power only when it's actually in park, allowing the start.

The STA wire isn't hooked up at all. To my knowledge this wire only tells the ECU that it's being started...and the schematic shows the wire leading to the starter. The truck does start fine without it, so I never thought to wire the thing up since the truck already has a starting circuit in it. So to connect this wire properly it would need power in the "start" position only? If that's the case, would there be any issue with tying it to NSW since it gets the same signal at the moment?

Now I know that this isn't the "best" way to do things, as it allows the truck to be started even when in gear. But as far as the ECU knows, it gets power to NSW and STA, letting it know that it's being started and that it's in neutral. Once started it looses power to those two pins, basically telling the ECU that it's no longer receiving a "start" signal, and that I immediately put the truck into gear. But what does it know, power to that pin is power to that pin. So what if the ECU is amazed by how fast I was able to put the truck in gear? :D
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
you say your using a sc engine and harness but a ls ecu...the connectors and ecus are different....how did you connect the sc harness to the ls ecu,did you cut off the sc connectors and splice in the ls ones maybe that's where the probkem is.
as for the kick down using the Ls kick down at the pedal is pretty easy to do
in our runners.i also used a micro switch at the throttle body on one swap.good luck man.
My LS had the 40 pin connectors, and plugged right in. Aside from the difference in the EGR system, everything else seems to have been the same so far.

Next time I'm at the junk yard I'm gonna pick up one of those KD switches and install it. Although I would think that it would be capable of a downshift into first without it.
 

rma

New Member
Messages
100
Location
san jose ,ca USA
Thats strange i have a few Ls ecu's and sc ecus none of them have the same connectors...and the ls kick down is a little different than the sc....well the base is different
and i found the Ls to be easier installed.
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
So I verified that STA and NSW both have 12v only when cranking. Yeah, NSW isn't hooked up to the shifter, but it's function is identical to the ECU. It thinks I'm in neutral until the engine is started, and that's all it really cares about anyway since there is no signal to it when driving regardless of how it's wired.

I verified that STP is wired correctly, and only gets 12v when stepping on the brakes.

I haven't wired the OD light up yet, but it's on the list.

BATT gets 12v always.
+B and +B1 get 12v when the key is set to "run" and "start"
MREL outputs 12v and triggers the EFI main, turning on the fuel pump when the key is "on" and "start"
IGSW gets 12v with "run" and "start"


I went through and de-pinned every wire on the ECU connectors one at a time so I wouldn't mix anything up and pushed the contact down to make sure that ever wire had good contact. The engine definitely idles lower now when cold. Right about 500rpms. Otherwise I can't tell that it's performance is any better at all.

I got sick of the tranny not shifting so I just wired the two shift solenoids up to a pair of toggle switches in the cab. Yee Haaa, what a difference having first gear makes. The stupid thing still isn't making the power it should though. Off the line there just isn't any torque at all, but once it gets up to around 3500 rpms or so it starts to pull OK, but nothing like 250hp should. It's all HP and no torque. :(

Still no error codes from the ECU...just a steady blinking light when I jumper TE1 and E1.
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
Thats strange i have a few Ls ecu's and sc ecus none of them have the same connectors...and the ls kick down is a little different than the sc....well the base is different
and i found the Ls to be easier installed.
You know, thinking back to it now, I pulled the engine and ECU from an LS planning on running that drivetrain, but ultimately changed my mind and bought an SC motor on Ebay because I wanted a newer low mileage motor to start with after having so many problems with my previous 7M series swaps in this truck.

So I ended up picking up an SC ECU at the junk yard when gather misc parts to do the swap. I do have two ECU's now though, and the engine doesn't run any different on either one. Albeit they are both junk yard ECU's.

Given the failure rate of these computers though, it wouldn't surprise me to learn that both of them are bad. I have pulled the covers off of them though, and neither of them look like the caps are blowing out though.

Anyone have an ECU that they have personally tested to be working properly they wanna sell? Or does anyone wanna test mine if I ship it to you? Aside from replacing the primary 02 sensors, the ECU is looking like the problem...I've checked everything I can think of on this thing.

First thing tomorrow morning the truck goes to the smog referee, so hopefully it passes there and I'll actually be able to road test this thing again without fear of the local P.D.

I'm thinking that once I get a known good ECU in there, it's either gonna work like it should....or one of you lucky 1UZ guru's is gonna get a paid vacation to california to sort it for me. :D
 

gloverman

Well-Known Member
Messages
2,968
Location
Hamilton. New Zealand
Yep. Going from your description its wired wrong. Main relay isnt for the fuel pump. 40/40/40 ecus trigger the fuel pump via a separate fuel pump ECU. I think its important to have the pump turn off if the engine is not running. Also bet it doesn't idle up consistantly when started.
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
Yep. Going from your description its wired wrong. Main relay isnt for the fuel pump. 40/40/40 ecus trigger the fuel pump via a separate fuel pump ECU. I think its important to have the pump turn off if the engine is not running. Also bet it doesn't idle up consistantly when started.
I thought about installing the fuel pump controller when I putting the LS fuel pump in the truck. Seems a lot of people have problems with the controller failing, and while I know I could hotwire the pump on the side of the road, it just seemed like something extra to fail on the truck. I don't put many miles on this thing, maybe 1000 or so a year, and at that rate the pump would last forever even running at full speed all the time.

The pump is powered through the circuit open relay in the truck, using MREL, the EFI main relay, and the circuit open relay. I did it this way because the entire system is already wired and in place in the truck when I did the swap.
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
Does the truck idle up correctly when cold?
It did until today. Now it idles just as slow cold as while warm. All I really did today was give STA 12v while cranking. I found that I had already wired STP and NSW last year when I first put the engine in. Granted that NSW isn't connected to the shifter, the ECU doesn't know the difference, as long as it's hot while cranking.

Other than that I just tested wires over and over again, stared at it, thought hmmmm, test some more, scratched my head some more, ect... Then I pulled every pin on the ECU and pushed the contacts down a little so that they had solid contact while plugged in just in case the pins were getting loose from being unplugged so many times. I did them all one at a time of course to keep them straight as I went. Kind of a PITA, because the contact is inside the pin itself, so you have to carefully push a pick inside the pin backwards from the inside of it. ...hard to explain, but makes sense when looking at the pins in your hand anyway. In all it really only took perhaps an hour.

When I get back from the smog referee tomorrow I'm gonna open up the ECU and look for leaking caps...and hope that I find some. At this point I don't even care if it's an easy, or cheap fix...just finding a problem would be a relief. So far all I get is symptoms.
 

gloverman

Well-Known Member
Messages
2,968
Location
Hamilton. New Zealand
Wire the main relay (and stepper) correctly and that should help the idle. Do you have the gear selector inputs wired? shouldnt effect power but getting the basics right is a good starting point. Have you checked which rear speed sensor(SP2) you have got? 2 or 4? Have you checked the ignition timing? at idle , revs and under load? what about wiring it for live data?
 

a7mgte

New Member
Messages
22
Location
Morro Bay, CA
I'll look more into the EFI main circuit tomorrow as well. There are only two stepper motors I can think of on the engine, the EGR and the ISCV. The ISCV circuit hasn't ever been touched from the factory, and the EGR I wired up according to the schematic. It's only 4 wires to the ECU and two for power.

The rear speed sensor was wired up with a 4 pulse sensor adapter on the mechanical speedo out of the tranny. Basically it's the one Marlin crawler sells for these swaps, but I figured out they are also on Honda passports and Isuzu Rodeos everywhere in junk yards for a couple bucks or less.

I haven't put a timing light on it, since it's not really adjustable anyway that I know of. But I guess I really should have anyway just to make sure the computer is doing it's thing properly. I did pull the timing covers and verified that the belt didn't jump a tooth. The belt looks pretty much new, and both the timing marks lined up perfect at 0 degrees like they should. I put in new caps, rotors, and plugs while I had it apart. Not sure how I could check the timing under load?

How would I obtain live data from an OBD1 system?
 

gloverman

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Messages
2,968
Location
Hamilton. New Zealand
I was refering to the SP2 pulse , not the Vss(SPD) pulse. Is it two or four?

To get data you will need to wire the under dash diagnostic plug and attach a suitable scanner.
 
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