High LTFT Cammed LS3

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02-10-2022
max_fear

High LTFT Cammed LS3

Hey all,

I am new to the tuning game and have always had my cars dyno tuned by a trusted shop by my house. This summer I had a stage 3 Texas speed cam installed, along long tube headers and a cai. After installing these mods, I had my car tuned by the shop down the road. Everything was great, until winter hit. I started to get a reoccurring LTFT lean code that would come on and off. I had HPtuners and logged to see what was up with the car. At first I believed it to be a vacuum leak because of it being in Bank 1 and 2, however I have found nothing that can lead to that. My fuel pressure is where it should be, and there are no exhaust leaks. Could something have changed with the tune? Does the colder weather have anything the do with the fact that I am seeing +20s LTFT ? I have logs if anyone would like to observe. Sorry if this is a nooby question. I am new to the tuning world.
02-10-2022
Cringer

Quote:

Originally Posted by max_fear

Hey all,

I am new to the tuning game and have always had my cars dyno tuned by a trusted shop by my house. This summer I had a stage 3 Texas speed cam installed, along long tube headers and a cai. After installing these mods, I had my car tuned by the shop down the road. Everything was great, until winter hit. I started to get a reoccurring LTFT lean code that would come on and off. I had HPtuners and logged to see what was up with the car. At first I believed it to be a vacuum leak because of it being in Bank 1 and 2, however I have found nothing that can lead to that. My fuel pressure is where it should be, and there are no exhaust leaks. Could something have changed with the tune? Does the colder weather have anything the do with the fact that I am seeing +20s LTFT ? I have logs if anyone would like to observe. Sorry if this is a nooby question. I am new to the tuning world.

Do you see the high fuel trims through out the throttle range? A vacuum leak would indeed appear on both banks, but a vacuum leak is really going to show at idle and on coast down where vacuum is high. Part and full throttle would minimize the symptoms of a vacuum leak. Did you make a histogram of fuel trims vs RPM?
02-10-2022
max_fear

For the most part yes, I do see them highest at idle (20s) and when cruising it will dip to around 15. I am not familiar with the histogram, but if you mean making the chart vs time on rpm and LTFT then yes. Looking at the chart vs time on my logs the LTFT jumps around very inconsistently with regard to my rpm.
02-10-2022
kevin87turbot

I would check the MAF. Make sure it's clean and free from debris or oil.
02-11-2022
Cringer

Quote:

Originally Posted by max_fear

For the most part yes, I do see them highest at idle (20s) and when cruising it will dip to around 15. I am not familiar with the histogram, but if you mean making the chart vs time on rpm and LTFT then yes. Looking at the chart vs time on my logs the LTFT jumps around very inconsistently with regard to my rpm.

Here is what I mean by histogram. I have included the settings so you can see and create your own. If there was a vacuum leak, the left side of the graph would be very large/positive numbers (adding fuel) and the numbers would trend down to near zero as it progresses to the right. In my example you can see the overall trend is pretty flat (near zero at all vacuum levels) which is what you want.

https://imgur.com/a/6A4q5ct