LTFT increasing with RPM/Load

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

T

Tinggi

Joined
Apr 9, 2021
Threads
5
Messages
20
Location
Calgary, Alberta
Recently had OTT tune done to my 2005 GX470.

Off idle, a lot more pull and no more transmission hunting on the freeway! Pretty impressive!

A couple of weeks later, I am more than happy with the performance increase! Fuel economy took a little hit but hard to say with the wild temperature swings we have been having. The next road trip will tell.

One thing I did notice that changed after the tune is that my LTFT, under load/increased RPM has increased dramatically! At idle the numbers are 3-5, at speed 12.5 to 14.4! STFT is pretty much the same as before, hovering at 0

OTT confirmed that the tune does not affect LTFT so now I am trying to identify the reason for the change!

Has anyone seen LTFT increasing with RPM/Load.

And after saying this it should be noted the motor runs without any issues! Smooth as silk on idle and highway speed. Lots of power!

Maybe I should just not worry about it till a CEL comes on!
 
So there is no explanation for LTFT increase under load? This increase is as RPM/Load rises and decreases as RPM/Load decreases! I always thought LTFT was historical data?
 
Non-zero fuel trims are usually due to O2 sensor, MAF, or vacuum leak-related issues. Total fuel trims (LT + ST) need to be +25% or -25% before they trigger a code. My rig has a YotaWerx tune and a aFe cold air intake and usually runs +10%. But, sometimes it will dip down to 0% or even slightly negative based on what appears to be things like running zero-ethanol fuel in it and even driving at lower elevations.

Personally I wouldn't worry about it. You'll go mad watching fuel trims all of the time. One tank of different gas can make a huge difference. If you do want to investigate it further, clean the MAF and replace O2 sensors (if they are original, it's probably time to replace them anyway) and see if it changes anything.
 
+lft means it's adding fuel because it sees lean conditions.
Not 100% Certain but lots of older GX fuel pump start to degrade after 200K miles. They pump a lot more fuel than fuel efficiency smaller cars.
Mine feels like it have muchm better power delivery after I changed the fuel pump. I was chasing weird ecu fault code last year and it end up my fuel pump is getting bad and pulling a lot more amps to run. It cause the fuel pump driver in the ECU to overload and end to fault mode. The problem is the code are so generic it does not point to fuel pump directly.
 
Very much appreciate the feedback!

1. Will stop watching fuel trims. No CEL so no worry at this point. Runs so much better sice OTT tune.
2. I will take a closer look at MAF. It was cleaned as first response to these numbers. No difference
3. Fuel pump will be checked when timing belt done next month.

Thanks

David
 
You must log in or register to reply here.

Share this page

Back
Top Bottom