Fuel Trims Advice rough idle

brendonsiX

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I dont think stft should go into the 20s or up in either variable unless you got a fuel issue.
Most quick forum searches show that stft will swing wildly depending on load and condition. On 27won blog post about it they state "You can expect max positive and or negative values under certain instances like flooring the pedal and heavy throttle lift off for example". I have the exact same numbers as you in that regard, as long as they are not constantly stuck at high numbers on stft I don't think it's a problem as far as I've understood from research.
 

kshawn

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That's what I'm thinking to. When you replaced yours all you got was the injectors and seal set and clips right?
I replaced mine to a aftermarket option. But yes. You'll need new injectors, clips, and seals from Honda.
 

brendonsiX

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At idle my ltft will reach in the -20s and at normal driving it averages about -10 -14
Ok gotcha, my LTFT goes back down to 0 at normal driving after maybe 5 minutes, if you're at -10 -14 you probably have a different problem like injectors as mentioned.
 


Jambles

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I'm experiencing something similar right now as well. I've had my prl street cai installed for the last few months and just recently picked up a Ktuner, but my STFT at idle sits at -8 to -15 on the factory tune and my LTFT shoots up to -10 if I sit for 15 minutes or so (I'm not sure how high it could go if I really sat idle long enough). I recently cleaned the maf and my filter to see if it was over oiled but the same thing occurs. I'm gonna try putting the stock intake on to see if its my prl intake causing this. Is it safe to say my fuel injectors are at fault if this persists after putting the stock intake on?
 

Neddih

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I haven't done anything to give me a reason to log again recently but I remember my ltft trims being off close to that amount I believe, and when I emailed TSP they told me it was fine. Ill try to dig up the conversation later, following either way.
 

alxgravel

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I'm experiencing something similar right now as well. I've had my prl street cai installed for the last few months and just recently picked up a Ktuner, but my STFT at idle sits at -8 to -15 on the factory tune and my LTFT shoots up to -10 if I sit for 15 minutes or so (I'm not sure how high it could go if I really sat idle long enough). I recently cleaned the maf and my filter to see if it was over oiled but the same thing occurs. I'm gonna try putting the stock intake on to see if its my prl intake causing this. Is it safe to say my fuel injectors are at fault if this persists after putting the stock intake on?
Maybe a start of an bad injector :S , honda changed all for free on mine was -25 STFT on idle
 

Jambles

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Maybe a start of an bad injector :S , honda changed all for free on mine was -25 STFT on idle
Yeah I agree. I put the stock intake on and the problem persists so I guess its fuel injector related. STFT at idle sits around -9 to -15 for me.
 

gtman

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Yeah I agree. I put the stock intake on and the problem persists so I guess its fuel injector related. STFT at idle sits around -9 to -15 for me.
Did you post the datalog? Right now I'd like to see what your LTFTs look like. STFT can fluctuate wildly. To me it's more about looking at the complete picture of your car at all speeds and throttle inputs, not just idle.
 


Jambles

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1Bristle

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Hey! Can I ask you what your numbers look like at idle? I have the same mods (race maf) and phearable tune with LTFT hitting -10 after maybe 5-10 minuted of idling but drops down quick when driving. Only thing I have is a injen hydro shield which I'm thinking might restrict my air flow a little.
My cars hitting near -10% ltft with prl race maf and the phearable tune
 

Daymon159

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Any news on this?

Having the same issue..

At idle it's -25 stft and -10 ltft with a 9.x to 10.x Afr

Light throttle is also -25 stft. Can hit full boost still, closer to 50% throttle stft goes now to -10 and then 0% at closed loop? Or is it open loop I can't remember lmao.
But on decell the car is popping and pulling timing and is still reading 10.x to 13.x Afr jumping around.

I'm getting very worried it's injectors going out.
The issue did pop the p0172 rich code, but a reflash fixed it for a few days. Then it came back. Cleaned the filter and reflashed and it ran perfect.. like better then perfect.
Week later it's running -25 stft all over again.

Any ideas? Was hoping it's just an o2 or plugs but there only 70000km on the car, and only 10000km tuned.

Really hoping Honda will take a look and figure it out but no dealer likes tuned cars ?
 

redcivic19x

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The people having wild fuel trims in the +/- 20 range should definitely get that figured out. But some of the other ones don’t seem that bad. My LTFT could be anywhere from -4 to -15 and my tuner said that was perfectly normally and he’s tuned A TON of modified Si’s and type r’s. I just always try to make sure my LTFT & STFT are always within +/- 10 of each other. That’s kind of my rule of thumb. I am also running an E40 + 93 blend. But it might be different for others since it looks like most people aren’t FBO yet.
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