Thread: LTFT's not locking in anymore

I had my car tuned about a week ago. The 2nd day after the tune the LTFT's started locking in at 5.3 when they are supposed to be at 0 like they had been doing. So i replaced the fuel filter since i had finished my first tank of e85 and disconnected the batter for 20 minutes. Reset the trims and they were locking at 0 again. Today as i was going to work, i got on it once and they locked in at 0. But at lunch i was coming home and got on it again and they were only locking in at 2.3. Whats the deal with them not locking in? Every now and then i will get blips of KR at like .2, .4 and .8 once but nothing higher. My wide band reads a 10.1 A/F and my o2's are at 950s. The guy that tuned it said the A/F is normal for running e85. help would be much appreciated.

not even reading your story, welcome to changing weather conditions.

also, FYI, your wideband is still reading in lambda no matter what so it will always read 1 lambda as 14.7:1. therefore the wideband should still read along the same lines as it would with gas. tell your tuner this. you are running super duper rich. id back it off to about 11.0:1.

i think im just gonna follow the powertuner handbook thing and tune it my self for my elevation. thats probably why im still eating through e85 pretty fast. how can i go about upping it up a little bit? like what changes and where do i make them? Shouldnt there be a stage where the maf should be unplugged while tuning? cause i thought the powrtuner handbook thing says that to make the car into open loop or something like that?

They say to unplug the maf when you do a VE tune.

Most of us don't do VE tuning at all/skip it.


Your fuel trims should lock in at 0 or close to 1 even if there is crappy weather. You are probably hitting parts of the MAF range that were untuned, due to either hitting PE and never disabling it during a maf tune or not a good enough scan to do the correct adjustments.

You want to start by disabling PE by setting the PE enable TPS to 100. After getting a GOOD scan, do your maf adjustments. I would do an adjustment, then reset fuel trims and do another scan and adjustment the next day. Either that or waste a lot of gas driving around through various throttle positions for 40 minutes with a few restarts in between.

After you've done this 2-5 times or however long it takes to get it damn near perfect, re-enable PE. Change the percents to something lower also, I think i have mine enabled at 20-25%. Either way, you want it lower than stock and it also helps to lock in fuel trims earlier, which sometimes helps it decide that it should lock in at 0 right ****in now.

As far as leaning the car out, you can either adjust the base PE afr then resetting the trims, or adjust it via maf table. Maybe subtract 3% from 8000hz on up or resort your scan by maf hz and see what areas need to be brought up or down. If you want richer, add. If you want leaner, subtract. Make sure to blend these adjustments so there are no jumps in the maf table either.

Ok so basically I scan it by rolling into the throttle on up to 100 kpa. Save the scan. Then how do I re sort the scan to maf hz? So are my trims always gonna lock in 0 all the time or they gonna adjust themselves again? My STFT locks at 0 but my LTFT is at 3.1 now. When I'm off the gas or idling, my LTFTs read 16.4. I know there is no vac leaks cause I've sprayed everywhere. The guy that tuned it said that's normal with e85. Is that true? Another guy replied to this thread on clubgp said its normal for the trims to read between -/+ 3 for compensation of fuel, is that true as well? I'm just confused because I'm being told mixed things.

Your trims will always vary a bit due to weather conditions. On my car, as long as it's within +/- 4 on my LTFT's I don't sweat it. They are compensating for air temp and pressure changes.

I can tell you that if you are going to try to get them to stay at zero, it's a rough road.

Also, anytime I have ever reset my trims and scanned immediately after... my LTFT's always look good. It takes awhile for the trims to get settled. If I reset, or upload a new file... I don't scan it again until I have drove for 30-45 mins.

Originally Posted by Lawngoose

Also, anytime I have ever reset my trims and scanned immediately after... my LTFT's always look good. It takes awhile for the trims to get settled. If I reset, or upload a new file... I don't scan it again until I have drove for 30-45 mins.

I will usually give it a couple of drive cycles for the trims to be relearned.

ok good that makes me feel alot better. i thought its a bad thing if they arent locking at zero. i still need to up the afr at tad bit so im not running so rich. how do i go about resorting the maf hz like fosho said after i scan?

Okay, are you logging with a wideband?

im not logging with it but i do have one. its at 10.0 when i go WOT with 940 o2's

Originally Posted by bbptech

im not logging with it but i do have one. its at 10.0 when i go WOT with 940 o2's

Do you have the HP Tuners Standard or Pro interface? You need to log MAF AFR Error % as MAF AFR Error % uses the wideband o2. If you have the Pro interface, you can hook the WB into it so it is all in VCM Scanner.

If the WB is showing 10.0 at WOT, you are running terribly rich. So much so that it can actually cause KR.

I should clarify that earlier when I said that you'll have a very tough time to get to 0%, I was thinking during cruising conditions, not at WOT. Like it was said, it should lock at 0% for LTFT's during WOT runs.

i never updated my sig. i actually have a powrtuner now.

Ya this is all stuff at WOT im talking about. at cruising my LTFTs read in the 15.6 to 16.4 range till i go WOT. The guy that tuned it said thats normal with e85. Before it was tuned they never touched 16.4 or even close. I know there is no vac leaks as i have sprayed everywhere with brake cleaner with no idle changes. From what i understand 16.4 usually means vac leaks.

yeah does sound like a vacuum leak..

but it cant be. Because i drove the car off the trailer with no 16.4. I know that because i made sure i didnt have any so there were no problems with tuning. He uploaded a bin file setup for e85, and basically the same tranny work. Is there a site that has the tables i need so i can retune this myself?

Sorry never got to your pm, I've been working from 8am-11pm the last 5 days.

You should post up something on the powrtuner forum, some people still check it.

If you don't already have UVscan or eddies table modifier, i would get them.

Eddies table modifier makes maf tuning really easy and is easier to sort your scans. I think the tuner notebook may explain how to maf tune using that program, but after the program makes the changes, be sure to view the change log and notice the differences it makes in the maf hz ranges and each other column.

To lean it out, I would import the scan into eddies table modifier to view the scan easier. This way you can sort it using maf hz, 02 mv, kr and so on. If you sort it by maf hz and see the upper 10k range or so and then see how that correlates to your 02mv, you may see where the 02 mv drop when you get lower in the maf hz. What you want to do is determine the maf range that your hitting and how far it should be raised. Say you notice the 02's are noticeably higher from 9000hz to 10500hz. What you would do is take 9000hz to 10500hz and subtract 3% or so from that range. (Subtract to take away fuel, add to add fuel) You also don't want any large jumps in the maf table, so you also take a few cells below 9000hz and you blend them, as well as a few cells above 10500. After you make the change, upload it and reset the fuel trims. I would then look at the wideband and see if there was a difference after making sure the fuel trims locked in at 0. Go from there in determining how much more to change or take away to lean it out. I would do it in small steps. You can't really rush maf tuning or tuning fuel in general or you will run into problems, patience is key.