Builds US Spec. February 1990 Poverty 80 2uz/h151f swap (2 Viewers)

[Tank5]

This project keeps going, it seems every time I solve an issue it presents a new one.

I was able to confirm the issue with the P0031 and P0051 codes. After pulling the harness off and opening it up I found the Air Fuel sensors battery power was never wired. It apparently got missed when the harness got built.

I after wiring it up and putting it all back together. Sure enough, no more P0031 and P0051codes.

Wiring it up.

With that solved I focused on what I believe was my last issue, the intake. What I have learned is that the factory intake is 3 5/16 inches ID, the same as the intake I had built. I have learned that the 2uz non VVTI and VVTI have different sized intakes. The non VVTI having a smaller intake.

The shop that built the harness sent me their MAF adapter which has the same ID. I ran a few different versions of the intake, varying MAF adapter, MAF location and cone filter size.

I set the intake up using a MAF adapter which is the same inside diameter as the intake I built. Set it with the cone intake filter. Took it for a drive and it is doesn’t have any power. I did get it up to 5th gear but then it completely lost power. It triggered two codes. P0171 and P0174. The A/F sensor codes did not come back though, so that is good.

I also tried removing the adapter and running my intake with the cone filter. It did not get any codes but it didn’t have any power.

For the heck of it I tried a smaller cone filter to restrict the air intake. Same thing, no power but did not get any codes.

Reviewing the P0171 and P0174 codes it identifies A/F sensors, MAF, fuel pump, fuel filter as possible issues. All of those have been replaced with brand new Toyota parts already. I have already gone through the hoses and intake gaskets looking for leaks and replaced almost everything with new.

These codes are are telling me to start over and go through everything again to figure out what got missed. I wondering if I have just looked over this thing so many times I am just not seeing the problem. I might have a blind spot.

 

[DivByZero]

Your current situation basically sums up the main reason I prefer mechanically injected diesel engines. My 1HZ doesn't know or care if I even have a battery.

 

[Tank5]

Your current situation basically sums up the main reason I prefer mechanically injected diesel engines. My 1HZ doesn't know or care if I even have a battery.

My previous 80 was a swapped 6BT Cummins/Nv4500 and I loved it except for the raw diesel smell that it emitted. It was almost problem free but not completely.

I have 2 other 2uz non-VVTI vehicles that run great. I expect this one will do the same when I get it dialed in. This swap has certainly had some challenges that should not have been. I will get it sorted eventually.

 

[thabruiser]

OK. Check your fuel trims when idling, and when driving. If you are/were getting lean codes, look at when it happens. If you are running fairly lean (on your FT, it will say somewhere above +10% FT for bank 1 and bank 2) at idle and especially with a load, you may be looking at a fuel delivery issue. Did everything go okay when you put the fuel pump together in the tank? Have you verified (with a mechanical gauge) the fuel pressure? IIRC, the 100 series had a 2 stage fuel pump. Is it possible you are wired just on the "low" stage? Just spitballing.

Good luck to you! And good job finding the B+ A/F sensor wiring issue.

 

[thabruiser]

Also, you said on post #104, you made or modified the fuel line to accept fuel from the passenger side. Is flow good through that modified line?

 

[Tank5]

Also, you said on post #104, you made or modified the fuel line to accept fuel from the passenger side. Is flow good through that modified line?

That line is a hard line connected to the original banjo fitting on the driverside of the fuel rail at the stock location. I blew it out before it was installed and after installed with the banjo bolt removed activated the pump to ensure I had flow to that point. It flowed well out of the banjo fitting. The line is not restricted anymore than the stock system was.

 

[Tank5]

OK. Check your fuel trims when idling, and when driving. If you are/were getting lean codes, look at when it happens. If you are running fairly lean (on your FT, it will say somewhere above +10% FT for bank 1 and bank 2) at idle and especially with a load, you may be looking at a fuel delivery issue. Did everything go okay when you put the fuel pump together in the tank? Have you verified (with a mechanical gauge) the fuel pressure? IIRC, the 100 series had a 2 stage fuel pump. Is it possible you are wired just on the "low" stage? Just spitballing.

Good luck to you! And good job finding the B+ A/F sensor wiring issue.

I cannot find a way to access live data with the techstream version I have. I am only able to get freeze frame data when trouble codes hit. I have not been able to reproduce the P0171 and 174 codes again. Although I didn’t have time to drive it tonight, so I am just running it in the garage.

I have hooked a mechanical fuel pressure gauge up many times through out the build as I have been working through the various issues.
The idling fuel pressure has Normally held at 42-44 on the mechanical gauge. I had hooked it up earlier this week and found the gauge was reading 38psi a little low, so I swapped the fuel regulator for another and got it back to 41psi.

When I hooked the gauge up tonight it was idling at 35psi.

I started thinking and decided to pull the vacuum line off of the fuel regulator to see what happened.

The fuel pressure bumped up to 45-46psi. I set my camera up to film the gauge while I operated the throttle. Through a series of reving the engine up to 4k rpm and holding steady throttle at 3k rpm the fuel pressure didn’t budge holding 45-46 psi.

The vacuum line I had attached to the fuel regulator runs to the bottom of the planum. Although the factory set up has the fuel regulator vacuum running to the intake tube. I figured a vacuum is a vacuum but may be they are not the same. I plugged the planum vacuum line with a nail and will put a cap on the regulator just to see how it drives. I will have to find a way to route the regulator vacuum to the intake tube.

Picture of vacuum line I am talking about.

I am hoping that maybe the vacuum was affecting the regulator so much it was reducing the fuel pressure too much. I will test drive it Friday if I get home early enough.

 

[thabruiser]

I was curious about that FPR line. The factory routing of the line is before the throttle plate, like you said, which theoretically means that it is not "vacuum," though it may less than atmospheric due to the suction of air down the tube. So at idle, with throttle plate closed, you have very little suction down the tube pre-throttle plate, or low "flow." You will also have high vacuum. At higher RPM, with throttle plate open more, you will have higher "flow" of air, pulling the diaphragm of the FPR more so than at idle. In theory, your FPR was working the opposite way it is designed to. That may be why it has had a hard time off idle to run smoothly. Also, out of curiosity, where are you tapping in to see the fuel pressure?

As a side note, if you have Techstream, you should also have access to the live data.
Enter the following menus from the main page of Techstream: Powertrain / Engine and ECT / Data List
That should show you everything "live". There may be a tutorial on YT if you are unsure how to get there.

 

[Broski]

Very impressed with your ability to keep after this Issue Denis and the way the community jumps in to help !!
Great build !

 

[Tank5]

I was curious about that FPR line. The factory routing of the line is before the throttle plate, like you said, which theoretically means that it is not "vacuum," though it may less than atmospheric due to the suction of air down the tube. So at idle, with throttle plate closed, you have very little suction down the tube pre-throttle plate, or low "flow." You will also have high vacuum. At higher RPM, with throttle plate open more, you will have higher "flow" of air, pulling the diaphragm of the FPR more so than at idle. In theory, your FPR was working the opposite way it is designed to. That may be why it has had a hard time off idle to run smoothly. Also, out of curiosity, where are you tapping in to see the fuel pressure?

As a side note, if you have Techstream, you should also have access to the live data.
Enter the following menus from the main page of Techstream: Powertrain / Engine and ECT / Data List
That should show you everything "live". There may be a tutorial on YT if you are unsure how to get there.

The more I thought through the effects of FPR line hooked up after the throttle body versus before I could understand why it would be problematic. Although your explanation really helps it make sense. It would be great if this solves the issue.

Thanks for the tip on the Techstream. I will follow your directions and see if I can access the live data tonight and report back.

I am reading the FP through a fitting I installed on the front passenger side fuel rail banjo joint.
Pictured.

 

[Tank5]

Very impressed with your ability to keep after this Issue Denis and the way the community jumps in to help !!
Great build !

Thanks, The help and shared information that comes from this forum are certainly an enabler. It really is an invaluable resource for a backyard hack such as myself. I expected a simple motor swap in comparison to the 45 build would have gone pretty quick but this build had its own set of issues to work through. Admittedly this build was not always the priority as I set it aside to finish then enjoy the 45 for a bit.

I really want to have this running and driving properly before the end of May and have put off a few follow up projects on the 45 until this runs and drives, so I can stay focused on it. I feel close.

 

[Tank5]

I drove the truck once which was enough to confirm the vacuum vacuum line was not the issue. It feel underpowered and the P0171 and P0174 codes came back within a mile of pavement.

Here are some freeze frame data points from the the trouble code.

 

[Tank5]

@thabruiser Thanks for the directions. I thought I had clicked on the data list button before but I guess not. Here is some live data idling in the gauge. If you don’t mind telling what data to focus on specifically I would try to capture it while driving under load. As a comparison.

 

[Tank5]

I learned something new from the harness builder. He suggested that I may need to recalibrate the throttle body with the pedal. I have disconnected and reconnected the battery from the harness more than 50 times in my efforts to troubleshoot things and make any changes to the harness. He said it is possible that the throttle body is not calibrated to the pedal.

I set up a camera and watched the throttle body and sure enough it was not opening up all the way. He sent me re calibration directions. I tried this once but it was not successful. I will have more time to try again tomorrow to see if it works. I am adding the calibration directions should they help someone else out. And make it easier for me to find again.

Throttle Calibration:

When you replace the computer (ECU) on your Toyota and the throttle doesn't open fully—resulting in issues like rough idle or poor throttle response—it often means the new ECU hasn’t yet “learned” the proper throttle range. While Toyota’s official service information may not list a specific throttle relearn procedure for every model, many owners have found that a dedicated relearn cycle after such a replacement can help restore proper throttle operation.
Step-by-Step Throttle Relearn Procedure

1. Prepare the Vehicle:
   • Battery Check: Ensure your battery is in good condition and properly connected. (Some technicians recommend briefly disconnecting the battery for over a minute to clear any residual adaptive values before starting the relearn process.)
   • Clean Environment: Make sure the throttle body is clean and that all electrical connections, especially to the throttle position sensor (TPS), are secure.
2. Ignition On, Engine Off:
   • Insert your key and turn it to the “ON” position without starting the engine. This will activate the ECU and related throttle control circuits.
3. Accelerator Pedal Cycle:
   • Fully Depress and Hold: Press the accelerator pedal all the way to the floor and hold it down for about 40 seconds. This extended hold lets the ECU register the maximum travel range of the throttle.
   • Release Gradually: Slowly release the pedal completely.
   • Repeat the Sequence: To ensure consistency, repeat the full-press and hold cycle about 3 times. Some variations call for slightly decreasing hold times with each subsequent cycle (for example, 40 seconds, then 30 seconds, then 20 seconds) followed by short pauses in between.
4. Turn Off and Restart:
   • After completing the pedal cycles, turn off the ignition.
   • Wait a few seconds, then turn the key back to the “ON” position and start the engine.
   • Let the engine idle for at least 10 minutes so the ECU can adjust to a stable idle speed and fully incorporate the new throttle range settings.
5. Test Drive:
   • Once the idle stabilizes, take the vehicle on a gentle drive. The ECU will continue fine-tuning the throttle response as you drive. Monitor for any abnormal behavior like hesitation or erratic idle, which might indicate that further troubleshooting of sensors or intake components is necessary.

---

Why This Procedure Works

• Adaptive Learning: In modern drive-by-wire systems, the throttle body is controlled by a servo mechanism. The ECU learns the full travel range of the throttle during these cycles. When you replace the ECU or clear its memory, these learned parameters are lost.
• Calibration Reset: Performing these cycles “teaches” the ECU the proper end points for a fully open and closed throttle. Even though some Toyota models recalibrate automatically after replacement or battery reconnection by simply driving for a few miles, executing this procedure may accelerate the process and ensure optimal performance.

 

[RivMan]

Your Long Term Fuel Trim is pretty much maxed out.

Basically the MAF sensor reading is extremely low compared to the air actually entering the engine, causing the ECU to under-fuel.

The ECU corrects that by reading the O2 sensors, and adding fuel until they read correctly (Lambda=Target Air-Fuel Ratio). In your case, it's adding 39.8% more fuel than the calibration says it needs based on your freeze frame data. You really want LTFT to be close to zero, no more than ~5% typically.

Possible causes:
(Large) Vacuum leak
MAF installed in a non-factory diameter intake tube
Bad O2 sensors (Not likely, there are two, and both are reading the same.
Bad MAF

-Rob

 

[thabruiser]

Your long term fuel trim for bank 1 and bank 2 are primarily what you need to be looking at. You are, according to your data list, running way too lean. Your injectors are, right now, attempting to richen up the mixture by almost 30% overall (i.e. Long term, or LTFT), and your short term (STFT) is at 7-10% more, bringing the total for each bank to almost 40%....For reference in my experience, Toyotas like to see +/-7% TOTAL. So, you can run 0% STFT, and +/-7% LTFT, 3% STFT and -10LTFT, etc. It varies all the time based on your quality of fuel, but a healthy-running engine will typically stay under 10% total fuel trim. (I know this may be confusing, so sorry if it doesn't make sense. It is kind of an experience-based diagnostic you develop over time...)

The short of it is, you need to figure out why you are lean. Again, this is based on how I have found it works. If you have a lean condition at idle (read: STFT and/or LTFT is high positive) that seems to get better (closer to 0%) with throttle, then you likely have a vacuum leak. When throttle is closed, you have max vacuum, when you introduce throttle input, vacuum decreases. So if it is a vacuum leak, your "leak" lessens proportionally to vacuum decreasing.

Conversely, if your lean condition is not changing with throttle input, or gets worse, then it is possible (not a guarantee....there are no guarantees in vehicle diagnosis except that you are usually wrong...haha), that you have a fuel-side issue. Either poor quality of fuel (i.e. water in fuel, or excessive ethanol content), or a fuel delivery issue (fuel pump, FPR, kink in a line, injector(s) blocked, etc).

So I'd say first, try and figure out if it is a vacuum issue, or a fuel delivery issue. Vacuum leak can be found by spraying brake cleaner (i know some have used map gas, but i never have) around possible sources of vacuum leak to see if, when you do, the fuel trim numbers start to "correct" themselves . In other words, If there is a vacuum leak and you introduce a combustible vapor into that leak, your fuel trim numbers start to go down as it is introduced into the system. For example with yours, if your throttle body gasket was leaking, and you spray brake cleaner at the gap where it meets the intake manifold, your fuel trim numbers would begin to change from positive numbers, to negative numbers, as it is reducing injector "on time" to compensate for the extra fuel it is seeing being burned in the combustion chamber and flowing past the new A/F sensors you just put on

Additionally, your fuel trim number suggest that the vacuum leak or fuel issue is not on one side of the engine or the other. If it was, you would only have whacky fuel trim numbers on one bank. You may try pinching off random vacuum sources, and see if you get anything to change. Purge VSV's, secondary air VSV's, I have also seen brake booster check valves cause lean codes. How sure are you that your intake tube is airtight? Things to consider. Sorry so long. Good luck to you!

 

[onemanarmy]

I've never experienced this level of troubleshooting, but its all fascinating!

Hope we get to the bottom of it soon!

 

[Tank5]

@RivMan , @thabruiser , Thank you! for the diagnostic read and tech advice. I will have to read it a few times to make sense of it and work through it.

Not that I haven’t missed something but here is what I did to work through some of the possible causes mentioned.
Vacuum leak:

• Replaced planum to head gaskets with new oem
• Replaced all vacuum hoses with new except two that appear to be good condition.
• Used brake cleaner to look for leaks around the intake, planum, and hoses.
• I also used a bore scope to look under the planum to see if any of the gasket appeared out of place or created an irregular gap.

MAF:

• Ordered new OEM MAF sensor
• The air intake currently pictured is built from a K&N cold air intake for a 2005-2006 tundra that has the same 2uz VVTI motor. So the intake tube and filter are are spec. For this engine from a aftermarket company big enough to get it running right. I hope anyway.
• The intake couplers are all tight with clamps and I could not find any leaks around them.

Fuel system:

• Brand new OEM filter
• Brand new OEM fuel pump for this specific engine
• Cleaned out a very clean fuel tank when I replaced the fuel pump. It was really clean inside to begin with, so not much to clean.
• Fuel pressure was swapped from another running 2uz.
• Fuel pressure monitored and confirmed with a mechanical gauge and camera. Fuel pressure holds strong 45-46 psi, especially after I corrected the vacuum line routing on FPR.
• Replaced both A/F sensors with new Toyota oem units. Then diagnosed and resolved a wiring issue in the harness for said sensors.

I realize that just because I bought new oem parts it doesn’t mean they couldn’t be bad. I am currently forging ahead as if that is not the case.

I also realize that maybe I missed something I already cleared or believe is good like vacuum leak. I cannot hear anything that sounds like a leak and got no reaction from the brake cleaner test. I will go back and try this again though. I don’t have an oem air filter box to hook up to this to see if that would make a difference and buying one is an expensive test. The intake I have is built for the motor but I could ultimately try to swap it out for another to see if that is an issue.

I method at the moment is to continue working through and solving issues as I find them. This week I have been focused on the throttle body. I wanted to confirm the throttle body was functioning properly but found that it is not.

To test the throttle body, I set up a camera to watch it while I turned the ignition on but didn’t start the engine. I worked the throttle pedal three times all the way to the floor and back. I found the throttle body plate is only opening half way.

I spent the last three night working through the throttle position relearn process multiple times and with no secure turned to YT for other relearn process and none of them have corrected the throttle position. In other words it not opens half way. There were a couple couple time when the first throttle pedal press opened the plate all the way but the following presses it not opened half.

Tonight I have unhooked the battery and unhooked the ecu. I am going to install a new oem throttle position switch. After leaving everything unplugged for a couple hours I will put it all back together and try to run through the relearn process in hopes that it all gets a fresh start.

If that doesn’t work, I might get wonder if the throttle body is bad and try to find a bench test for it if so.

 

[RivMan]

@RivMan , @thabruiser , Thank you! for the diagnostic read and tech advice. I will have to read it a few times to make sense of it and work through it.

Not that I haven’t missed something but here is what I did to work through some of the possible causes mentioned.
Vacuum leak:

• Replaced planum to head gaskets with new oem
• Replaced all vacuum hoses with new except two that appear to be good condition.
• Used brake cleaner to look for leaks around the intake, planum, and hoses.
• I also used a bore scope to look under the planum to see if any of the gasket appeared out of place or created an irregular gap.

MAF:

• Ordered new OEM MAF sensor
• The air intake currently pictured is built from a K&N cold air intake for a 2005-2006 tundra that has the same 2uz VVTI motor. So the intake tube and filter are are spec. For this engine from a aftermarket company big enough to get it running right. I hope anyway.
• The intake couplers are all tight with clamps and I could not find any leaks around them.

Fuel system:

• Brand new OEM filter
• Brand new OEM fuel pump for this specific engine
• Cleaned out a very clean fuel tank when I replaced the fuel pump. It was really clean inside to begin with, so not much to clean.
• Fuel pressure was swapped from another running 2uz.
• Fuel pressure monitored and confirmed with a mechanical gauge and camera. Fuel pressure holds strong 45-46 psi, especially after I corrected the vacuum line routing on FPR.
• Replaced both A/F sensors with new Toyota oem units. Then diagnosed and resolved a wiring issue in the harness for said sensors.

I realize that just because I bought new oem parts it doesn’t mean they couldn’t be bad. I am currently forging ahead as if that is not the case.

I also realize that maybe I missed something I already cleared or believe is good like vacuum leak. I cannot hear anything that sounds like a leak and got no reaction from the brake cleaner test. I will go back and try this again though. I don’t have an oem air filter box to hook up to this to see if that would make a difference and buying one is an expensive test. The intake I have is built for the motor but I could ultimately try to swap it out for another to see if that is an issue.

I method at the moment is to continue working through and solving issues as I find them. This week I have been focused on the throttle body. I wanted to confirm the throttle body was functioning properly but found that it is not.

To test the throttle body, I set up a camera to watch it while I turned the ignition on but didn’t start the engine. I worked the throttle pedal three times all the way to the floor and back. I found the throttle body plate is only opening half way.

I spent the last three night working through the throttle position relearn process multiple times and with no secure turned to YT for other relearn process and none of them have corrected the throttle position. In other words it not opens half way. There were a couple couple time when the first throttle pedal press opened the plate all the way but the following presses it not opened half.

Tonight I have unhooked the battery and unhooked the ecu. I am going to install a new oem throttle position switch. After leaving everything unplugged for a couple hours I will put it all back together and try to run through the relearn process in hopes that it all gets a fresh start.

If that doesn’t work, I might get wonder if the throttle body is bad and try to find a bench test for it if so.

Thanks!

A couple things to look at with your throttle behavior:
The scan tool will show Accelerator Pedal Position (APP) as well as Throttle Position. There may also be a Desired or Target Throttle Position. There isn’t a 1:1 correlation between those. At idle or cranking, you may only get half throttle for full APP. The throttle system is VERY sensitive to faults. If that was your issue, you’d see a trouble code for it very quickly.

I’ll try to take some data from my 06 4Runner, to see where my MAF and MAP readings are compared to yours.

-Rob

 

[thabruiser]

Another thing I do when I'm suspecting a faulty part or something seems to be not operating as I expect, is to go look at a known good vehicle that runs fine and has no issues. If you have access to another 4.7 v8 that runs just fine, (I didn't see if you had one or not at your disposal), look at how the throttle plate operates on the known good vehicle. There have been many times I headed off condemning, (and replacing) parts unnecessarily by double checking normal operation of said part on a known-good vehicle. In fact I did that yesterday with an A/C pressure sensor on a Camry! IIRC, most throttle plates on Toyotas do not open 100%. But I may be wrong. Probably am.

I do not do what the harness builder said as far as learning throttle position. The way I understand (in practice) Toyota's throttle learning, is as follows:

A) When you disconnect the battery, and reconnect, the ECM goes back to a base learned value, preset at the factory. This is why a lot of times, if you disconnect your battery, battery dies, etc, and you don't clean the throttle body, you will have a rough or too low of idle, due to the throttle plate going back to 0% learned opening. If there is carbon buildup on the plate or throttle body, that is.
B) Each time you start the vehicle, it attempts to learn idle, and tries to reach it's target of 800rpm when warmed up. It will open (or close) the throttle plate a little, and tries to see what is satisfactory for the A/F ratios. In effect, a clean throttle body on a cold vehicle may start out at 1500-2000 rpms when started. You can watch the ECM try to bring that RPM down, but it will (in my limited experience) not do it in the first key cycle, even if warmed up to operating temperature in that key cycle. It will get pretty close. But especially older Toyotas, it takes several key cycles for the ECM to learn how much throttle plate opening will get the desired idle.

Here is how I help the ECM learn throttle and idle after a battery disconnect, ECM replacement, or throttle body cleaning:

1. Start vehicle, let it run 5 minutes with no accessories on (lights, blower motor, or radio). Idle is usually around 1800-2000rpm, and will slowly come down to about 1200-1500rpm. You can kind of watch it stop bringing it down. It will edge it down a little, and then stop. Eventually it won't move it down anymore.
2. Turn vehicle off for about 30 seconds.
3. Restart vehicle. let it run for about 3 minutes. Usually this gets it pretty close. By this cycle, it will be anywhere from 1200-900rpm.
4. Turn vehicle off. Let it sit for about 10 minutes.
5. Restart vehicle, and drive it on a short (5 miles or so) trip. For me, this is 4 stop lights, and a short stint on the I40. Each "stop" event in "D" (brakes applied, idling at a stop light, transmission in "Drive") also aids in learning idle. The highway run gets it up to operating temp and helps the ECM better gauge throttle plate ideal position.
6. If everything went well, it should be NEARING base idle, or 800rpm. Some do it right away, (newer Toyotas learn pretty fast) some take a few cold soaks before fully learning base idle.

I'm sure others have way easier, way more professional ways of doing it, and I am not saying my way is the only right way. It's just how I do it, and it works for me across the board for Toyota. Until the next one I work on, which will throw this all out the window. haha....I love my job!

Let us know what you find, and good luck.