High idle LTFTs, good otherwise

[mattgw86]

So I'm working on my tune for my hotcam and my LTFTs driving around and cruising are ok- ranging from around 125-132. Mostly right at or near 128. My LTFTs at idle shoot straight to 160. The STFTs are in the 140s at idle too. I've checked for vacuum leaks, fixed a couple exhaust leaks, and replaced a failed O2 sensor so far.

It smells like it's running real rich at idle too, just like my stock tune did before the cam swap.

I'm finding conflicting information regarding fuel tuning. I'm seeing people say to adjust the VE tables, and others saying that'll do nothing. Everything in my fuel system is stock and I'm running a K&N CAI, LPP long tubes, Magnaflow cat back with the hotcam and 1.6rr. Where do I need to go to get my idle fuel trims back in line? I can post a scan 94/95 log later if needed.

Thanks in advance.

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[zoomo]

i never have been able to get mine down either. I did a lot of reading and tinkering trying. check out gearheadefi they have some good info on there for "$EE" tuning.
The only tuning thing i ever did that seemed to make a noticeable difference in the idle fuel trims was when i finally adjusted my maf. I ended up having to richen up pretty much the whole range about 10% and in the process brought up the low range about 5% or so to make the curve look good. Now they run about 140 and 150 at idle.
They were showing up split like 10 or 20 driving at one point and it ended up being the intake manifold. i tightened it up and straightened that out, make sure you have it plenty tight and torqued in sequence.

As far as tuning the ve, i still havent done mine. My cam is sort of like the 503? i increased my entire ve table 10% because that seemed to be the going rate on everything else. (make sure that increasing it richens it, i would need to double check. ) From the reading i have done, the ve table will only come into effect if the maf is unplugged. Though there is conflicting information there, some people say that it is used even with the maf.

Now as far as tuning the maf. This greatly helped my cruising blms, idle blms, tip in response, fuel mileage, etc.
with a wideband, i had the best luck setting the entire open loop table to 13.5:1 or something around there, disabling both closed loop and PE entirely, and just do some driving. You want to adust your maf tables until your wideband hangs out where it should. You will have to do it a few times to get it right. I may be saying this wrong check out my thread on it here.
http://www.gearhead-efi.com/Fuel-Inj...and-idle/page3
Go to page 2 and three and pay closest attention to steveos and my posts.

Im not sure this is the correct way to do it, and i take no liability, but it worked for me !! haha

[mattgw86]

Yeah, I really need to get a wideband. Hopefully I can get my idle right and get myself close enough for the time being.

Which tables exactly are you messing with in tuner pro? Not the MAF calibration, right?

I think I actually signed up on gearhead efi a while back. I'll go do some reading there and see what I can find.

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[zoomo]

Yes you adjust the maf calibration to tune the maf. It has three tables, the numbers on the left are pretty much irrelevan to us. The numbers on the right match up with the airflow reading at different rpms, loads etc. I think it's like airflow grams? I can't remember what it calls it. I will check later. Anyway, if you adjust it up, it thinks it's getting more air so delivers more fuel and vice versa.

[zoomo]

I'm no expert by fat, maybe someone else can give an opinion on this. I'm just wondering, without a wideband, I don't see why you couldn't use the stft to adjust the maf. Of course it wouldn't work for adjusting high airflow at wot but it would give you an idea. Mine was fairly linear , prettyuch 10% richened through the whole thing. I tweaked it to make it pretty but it was easy to get close

[Injuneer]

In closed loop, the STFT's are constantly, rapidly changing. The PCM is constantly toggling them back and forth between slightly rich and slightly lean. It does that to make the cat work, storing oxygen when the exhaust is lean, and using the oxygen to oxidize unburied HC's and CO when it's rich. If the LTFT is stable, the STFT will average 128. If the STFT is spending too much time on the rich side, the PCM increases the LTFT to pull the STFT back down to an average of 128. That's the "learning" that takes place.

With a moderate cam, make sure there isn't something else causing the O2 sensors to read lean, resulting in high LTFT's. Do that before you reach the point of altering the MAF calibration.