Builds US Spec. February 1990 Poverty 80 2uz/h151f swap (4 Viewers)

[Tank5]

Can you post a log showing your fuel trims while driving?

A vacuum leak has the biggest effect on trims at idle, and the effect will lessen under load.

Thanks
-Rob

From I am advised, reading, watching a vacuum leak is at the top of the list for causing this issue. I just have not found one. I ordered a smoke machine as a last effort to identify vacuum leaks.

I am not sure how to create a log of my fuel trims under load but I do some research to try and figure it out.

 

[Tank5]

Also, if you haven’t read this thread, there’s a ton of good info there for troubleshooting a similar issue. I’m only on page 1, so I don’t know if he solved his issue.

2UZ-FE High Long Term Fuel Trims

I normally post in the GX470 forum, but this one seems to get a bit more traffic for the engines. I have an '07 GX470 with the 2UZ-FE and 138k on it. I installed a aFe cold air intake around a month ago and started getting PO101 codes for the MAF. I replaced the MAF (new Hitachi) and also found...

forum.ih8mud.com

Here’s another thing to check, from that thread:
“FWIW the MAF wiring is a possibility. My 1UZ does the same as yours but on the opposite side of the graph. Runs double digits in the negative trims until I floor it. At WOT it drops to about -5%. Whenever I monkey with the MAF plug the short term trim will immediately start to balance out the long term but after a few hours a driving it all settles rich again.”

-Rob

I did have to replace the MAF plug to resolve a low current MAF issue, which it did. It still could be a problem though. I really want to get past a potential vacuum leak before I have to dig through the harness again.

 

[Tank5]

While I am waiting for tools to arrive to continue working through the performance issue, I installed a rear bumper. Sad it does not work with the flaps but like it otherwise.

 

[Tank5]

My smoke machine showed up today. I tested for vacuum leaks, found two, one from the intake and the other from the brake booster hose. I found hints of smoke at the tube connected to the throttle body, so I swapped out the clamp for a better one. There was also a little smoke coming out of the hose from the vacuum line from the power steering pump added a clamp and no more smoke. Neither of these were the smoking gun I hoped to find.

I took it for a driver after sealing those two leaks and the engine did seem to run slightly smoother but it was still underpowered and giving codes for P0171 and P0174.

@RivMan you asked for a data log while under load. Best I could do was this shot from the live data while I was doing 60mph in 4th gear.

I ordered a fuel pressure gauge with a long hose, so I can watch it going down the road under load. That is my next test now that I feel I have ruled out vacuum leaks.

 

[Tank5]

My fuel pressure gauge arrived. Took the 80 for drive. Ran it hard up some hills and was able to get up to 80 mph. The fuel pressure gauge read 46 psi and never moved. It held that pressure solid, not even any slight bumps to the needle.

I don’t believe my lean issue is the result of fuel pressure.

I also ran through the Toyota diagnostic process for the MAF circuit. All tests were within spec.

Trying to determine what my next test is. I am thinking I may try to source an oem filter box and intake pipe to hook up to the engine to see if that might make a difference.

 

[Tank5]

I have also been stacked with an engine replacement in my Tacoma. I purchased a JDM low mileage replacement but have found I have to swap almost everything from the original motor to the new one to make it work. Waiting on the timing belt kit because the JDM water pump does not have a port for the oil cooler.



I purchased my Tacoma with low mileage engine and transmission rebuilds in it. Probably won’t do that again. I shouldn’t need an engine right now.

 

[06reg4x4]

Your maf reading seems high for idle. I can check the info at work weds. What ecu is this running off of? Stock exhaust manifolds? You’re at 20% short term fuel trims. That’s why it keeps popping the code. Maf diameter must match what factory was for the stick ecu. But seems you’ve figured that out.

 

[Tank5]

It seems like I may have made some progress. I cobbled this intake using an oem intake pipe with a MAF adapter as close to stock as I have. I used the used MAF that I had as a second n this set up. I will swap it with the new one to see if it presents any different.

These are are fuel trims after it warmed up.

Here it is WOT in third gear going uphill.

Here at 60mph WOT in 4th gear

Off throttle costing in 5th gear

I have ordered an oem filter box for this engine that I hope I can make fit.

I need to drive it more to make sure the codes don’t pop again.

This seems better but the engine is still very underwhelming. When pushing the pedal to the floor it doesn’t really respond. It kinda slowly builds speed but it is so bad I would have a difficult time passing another car if I wanted. It acts gutless. One of the only things I have not touched is the injectors. Do O need to test compression?

Thoughts for resolving underpowered poor throttle response?

Lastly, Big Thank You to everyone who has shared ideas and their expertise in helping me work through this. Hopefully I am past the lean issue

 

[RivMan]

Your ECU is still relearning it's fuel trims, but those screenshots look a lot better.

I'm not sure how volatile the memory is on these ECU's. I know I can manually reset trims with my tuner. You may want to see if disconnecting the battery for a while resets the Long Term Fuel Trims back to default, then see where it ends up.

-Rob

 

[Tank5]

Your ECU is still relearning it's fuel trims, but those screenshots look a lot better.

I'm not sure how volatile the memory is on these ECU's. I know I can manually reset trims with my tuner. You may want to see if disconnecting the battery for a while resets the Long Term Fuel Trims back to default, then see where it ends up.

-Rob

Thanks Rob,

I only drove it for about 20 minutes with this intake setup. I don’t know what it takes for the ecu to adjust to the changes I made. Thanks for the suggestion I will try disconnecting the battery for a bit to reset the system. I may not do this though until I have the oem filter box setup installed. I am hoping with that filter box it might even get a little better.

The MAF adapter I have is between 67-68mm ID and based on @Broski measurements I think oem is closer to 70mm ID. I am not sure how much this will affect the current results but it might. I don’t understand how the intake tube in my setup is causing these problems but it seems obvious it is. I used the filter and adapter before just attached to my intake tube and did not get these results, so I’m a little baffled.

Is your thought that if I reset the ecu it may improve the performance?

 

[RivMan]

It may.

The ECU learns fueling trims at each speed and load point. It takes quite a while at each point to learn how to properly run there. If you're moving through different points while accelerating, you could be hitting points where the fueling is way off, and not there long enough for it to learn.

-Rob

 

[06reg4x4]

What does the mad look like inside? Is it dirty?
Where the maf plugs in has to be the same size as what was factory on the ecu or you will have the issues your describing.

 

[Tank5]

What does the mad look like inside? Is it dirty?
Where the maf plugs in has to be the same size as what was factory on the ecu or you will have the issues your describing.

The MAF is clean and is a brand new Toyota part. I have a second MAF I got used that has been cleaned. It is the part in the intake just conked together.

What I find interesting is that the intake pipe I have is made from an aftermarket K&N cold air intake kit. All I did was shorten the pipe with all the hose mounts and MAF mount, then welded it to an allow that gave me the right angle to connect it to the 80 filter box originally. The K&N kit is made for a 2006 Tundra with the same 2uz VVTI engine. You would think of the intake pipe was too far off from spec. There kit wouldn’t work for any truck it would as on.

It does seem the intake pipe is causing my lean codes although I only drove it about 15 miles, so we will see after I get some more miles on it.

 

[06reg4x4]

Surprisingly we see a number of k&n equipped trucks with borderline lean codes etc cause of the design of the intake.
I have a 5.7 tundra that comes in with the big k&n kit and that this has all kinds of issues.

 

[Tank5]

Surprisingly we see a number of k&n equipped trucks with borderline lean codes etc cause of the design of the intake.
I have a 5.7 tundra that comes in with the big k&n kit and that this has all kinds of issues.

Given my circumstances that is reassuring to hear. Thanks for that!