Long term fuel trims at +20 - help

Replacing the upstream stock wide band this weekend

Then I guess I’m taking off my S/C and pulling the fuel pressure regulator and cleaning the injectors..I guess

Out of ideas

 

Update

Fixing vacuum leaks in intake tube lower LTFT from +20 to +10

 

I honestly dont know what's up with your truck (obviously). My Sc tuned up so nice with the Fic.

Pull the Sc and make it run stock, see where that goes. I just pulled my Sc too, just running turbo now. Gonna pull that soon to Ceramic all the hot parts and get some stock maf info. I actually have this issue where the truck will run super rich at barely part throttle on highway. Drives great, but barely push on gas and it will go to 10.0 to 1 afr. No fuel added in Fic in any category. So weird. I feel it has to do with blow thru maf.

 

Update

Replaced upstream stock wide band sensor. Truck is running much better now. AFRs drop to 13s right away at half throttle. 12s at wot.

Ready to start programming FIC!

Thanks @1997tacomav6

 

Update

Replaced upstream stock wide band sensor. Truck is running make better now. AFRs drop to 13s right away at half throttle. 12s at wot.

Ready to start programming FIC!

Thanks

 

LTFT are floating between 0 and +10 with the new stock wide band.

Replacing the throttle positioning sensor today for good measure oem

 

Remember OEM only

 

Bad trims can be any of these issues

 

I'd like to piggy back on this thread if I may (rather than starting an entirely new thread, since there's a lot of applicable info in here)
my truck - '04 3.4L SC'd about 20k miles ago, did the plugs and new fuel filter when installed, and just swapped to a 170 thermostat. Recently had a knock sensor code so replaced both sensors and the wire harness. So far so good, but got me thinking I may have some underlying knock issues (pretty sure I get the low RPM "lugging" ping, mildly at least)
Have a boost & AFR gauge to be installed soon, but was watching fuel trims on an OBDII scanner yesterday. I think everything looked pretty OK.

Feel free to correct me, trying to wrap my head around the values and what they mean:
Basically (I think) you want short term (ST) and long term (LT) to be close to each other and in a range of -10 to +10? (or is +/- 5 a more accurate range?) ST trims are constantly on the move, adjusting for fuel needs, either more or less to keep the 14.7:1 ratio. If they get to a certain point, either too far negative or too far positive, they "ask for help" and the LT trims make an adjustment so the ST trims aren't moving with too big of a swing in that direction. If your LT adjusts too far then you start throwing codes, say +/- 25 or greater?
The ST + LT = total fuel trim
so say ST is -3% and LT is 5%, your total fuel trim is 2%
I've seen a couple benchmarks written, that they should either be close to 5%, or 10%.
But, normal conditions, ST should stay pretty close to 0, +/- 5% or so, and LT should definitely stay +/- 10% (maybe less?)
Wide open throttle I think goes out the window as the computer is throwing fuel at it to enriched the mixture

Under partial throttle driving conditions yesterday mine looked fine. ST was at 0.8 and LT was between 3 to 5. The only odd blip was when I completely let off the throttle while decelerating to a stop, LT would jump to 18%, and ST would drop to -3 to -5%.
Not sure this is a big deal, and I need to get back out there today and double check what they are at idle while stopped.

One thing I read that I'm having trouble wrapping my head around is vacuum at idle. If the motor is pulling a vacuum (negative pressure) and outside the motor atmospheric pressure is 14 psi give or take, there is a "big" pressure differential between outside and inside the engine. IF I had a vacuum leak, then theoretically I would see a greater than expected value of air in the mixture, creating a lean situation, reflected by a large increase in fuel trims. But, this should be immediately reflected by a jump in my ST trims, not the LT trims if I'm understanding this correctly? or is the correction happening so fast that I'm seeing the result in the increased LT number?

Does the computer have different regions that will have different maps that show up i.e. while idle, partial driving? Just trying to figure out why I saw the big jump while decelerating only, and while driving things were more even.

 

You could overlay a throttle command graph with your short term graph and long term graph.

Your st will change as the throttle fluctuates...thats the purpose of a throttle. If your throttle is consistent, your fuel flow should be fairly consistent too. Your st will change instantly and the lt seems to take a minute or 2 before changing. I'm sure someone knows the exact timing of lt readings.