Long term Fuel Trim whacked out, with GRAPH

High all,
I have high (running lean) LTFT on bank 1 however, the STFT (short term fuel trim) seems to be manageable. The STFT for bank 2 is +/-5% and LTFT is about 3%.
As you can see my LTFT for bank 1 is around 20%. how can LTFT be so whack but STFT be more normal?
the only thing i can really suspect is possible throttle linkages out of sync or a vacuum leak but it idles perfect at 1050. i didnt do this test at constant RPMs "stages" (idle, 1.5k, 2.5k), i should have, but for now here is just a short test drive with graphing RPM (blue), bank 1 LTFT (gray) and bank 1 STFT (orange).
any ideas? as far as i know the injectors have never been cleaned or replaced. i would like to smoke test it, but with 20% its gotta be something obvious but i dont see anything. maybe ill pull the plenum in the next few days.
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i got code P1128 after a few hundred miles, which prompted me to do some diagnostics

 

yes it could be any of those things. i think ill just have to pull the plenum to take a look around, all exhaust bolts are tight and i cant hear any leaks.
its a 99, so obd2.

i did just do a major service along with some internal engine work and didnt have this code before. upon first start up and drive, i had the knock sensor and throttle body potentiometer plugs swapped by mistake. i wonder if from there something went wrong. ive read of that happening with no ill effects and ive done a full system reset since then, and it fixed the idle issues i was having due to the plugs being swapped, but now i have this LTFT issue on that bank 1.

 

Thanks. I didn’t put in new o2 sensors but I do have some I purchased last week. Was going to put them in anyway. No intake mods, only mod is capristo muffler and forza valve controller which all this data was gathered with it in normal stock mode. Stock headers, stock secondary cat pipes, stock cats although they were replaced a few years ago and are the spiral core type. I had everything apart to replace crank and rod bearings along with head work. There is a chance something isn’t put back how it was but I am quite methodical.
I do agree smoke test is my next step or regather the data on solid idle, then 1.5k then 2.5k to see if the trim levels decrease with higher rpm.
I guess my question is I thought ltft was determined from stft, how could it be so far off from the short term? What sensor is determining the long term?

 

I had exhaust leaks on initial start up because I didn't have all the exhaust post headers tightened up because I wanted to align bumper with muffler, but all those have been tightened since then and I've shut off battery cutoff switch a few times since then.

I unplugged battery last night then plugged it back in. Then started engine and logged data. The bank 1 long term trim was still through the roof and short terms were around zero at idle.

Maybe I just don't understand how long term trim works. I see short term as a real time check for the upstream O2 sensors and the long term as a average of previous short term values. But if I don't have anything crazy short term what is going on long term? I'm thinking I need to get long term reset somehow but don't you need an SD 1 or 2 for that?

 

any idea why long term would go from 20 to zero and back? short term does fluctuate +/-, its not always +.
im just going to tear the plenum off and see if i did anything stupid, but if the leak was that bad i would think it would raise my idle and be kind of obvious. same thing with exhaust leak, i would think i would hear it. Ive heard it before and its quite obvious. car idles and runs great, but i dont want to drive it like this until i figure it out.

 

see the gray line in the graph i posted. It is 20 most of the time, but drops to zero or close it, randomly. i dont get it.

 

well, maybe not randomly. it kind of seems like if i get on throttle harder thats when it slams to zero or so, but then when i let off throttle it spikes...that would tell me a vacuum leak. i am going to pull this plenum first. or maybe ill hook up my boost leak tester to the plenum and see if i hear any air leaks.

 

oh really? thats interesting. my spreadsheet was corrupt this morning otherwise i would provide more data on bank 2, which looks fine on long term and short term.
what would be so specific to bank 1 causing this kind of a fuel trim? i wish there were an easy way to test fuel pressure in one bank.

 

correct, 2 regulators.
i would think if there was a leak maybe at one of the throttle bodies on bank 1 it would only make that bank/cylinder lean and not affect bank 2 at all, but maybe i have that wrong.

someone needs to make an inline gauge adapter for the flared fittings for the fuel inlet so i can test the pressure on each bank.

 

ill drop the new O2 sensors in tonight and see what happens. after looking at even my STFT in the graph, they probably should be switching up and down more often.

 

i would think they would be clogged if anything on bank 1 since its running lean and overcompensating via increased pulse width. the O2 sensors may be lying so im going to swap those first and see.

 

i swapped the secondary o2 from one side to the other, i still see lean measurement on the 2ndary o2 sensor on bank 1. i also replaced the upstream o2 on bank 1 with no change.

although...i was playing with the throttle linkage and noticed that if i barely move it, there is some play on the driver side and linkage doesnt move, however the passenger side opens a little. and with linkage fully open the mechanical stop hits first on the passenger side. so from what im seeing, the linkage may be out of alignment? it also must affect idle because my LTFT is messed up at idle too.