LTFT's on Rebuild

[FlaBouy]

OK guys, I have hit a wall. I have a 2004 Avalanche Z-71 with a 5.3L. I have a Vortech S/C on the truck and have run HPTuners since December. Truck ran great with exception of GM 8.1L Marine injectors were showing115%-120% duty cycles. So while I was installing the 60# injectors, I decided to add a set of Stage 2 heads and a cam. I rescaled the injectors, tweaked the VE tables, and made adjusments to PE on the dyno. Dyno'd at 500RWHP 492 ft lbs. I noticed that when I reflashed the PCM and started the truck for the first time the LTFT's were 25% but the stft's were single digit and adjusting under throttle so we went to the dyno without retuning the VE tables.

When I try to adjust the VE tables to cure LTFT's the truck stumbles and idles rough. I put the tune back into the truck that we dyno'd with and truck drives fine, accelerates great, and has overall good performance. I show a little KR but I don't know yet if the sensors are picking up the cam. May have to adjust the sensitivity..The problem is when driving around the truck throws P0171,P0174, and P0300 SES codes and the LTFT's will show 25% at idle and around 15% under load. I thought initailly I had a vacuum leak or air leak and I tore the truck back down from the CAI to the TB. My Vac/Boost Guage shows -18" and I still have idle RPM up in the 800 RPM range until I solve this. I added a GSS341 Walbro a few weeks prior to the injector/head/cam swap. I run Pacesetter LT's, no cats and a Magnaflow. I also run a water/meth kit until I get an intercooler built for the Vortech. I also run a 2600 stall.

Any suggestions on why the LTFT's are all out of sorts. What would cause them to change from idle to mid-rpm and then back at idle.....

I am attaching tune and log. Be easy. This was my first tune in a motel while the head and cam was being installed. I was guessing at most of this and was actually surprised when the truck fire and idled in as smooth as it did with the cam and heads....

[S2H]

OK guys, I have hit a wall. I have a 2004 Avalanche Z-71 with a 5.3L. I have a Vortech S/C on the truck and have run HPTuners since December. Truck ran great with exception of GM 8.1L Marine injectors were showing115%-120% duty cycles. So while I was installing the 60# injectors, I decided to add a set of Stage 2 heads and a cam. I rescaled the injectors, tweaked the VE tables, and made adjusments to PE on the dyno. Dyno'd at 500RWHP 492 ft lbs. I noticed that when I reflashed the PCM and started the truck for the first time the LTFT's were 25% but the stft's were single digit and adjusting under throttle so we went to the dyno without retuning the VE tables.

When I try to adjust the VE tables to cure LTFT's the truck stumbles and idles rough. I put the tune back into the truck that we dyno'd with and truck drives fine, accelerates great, and has overall good performance. I show a little KR but I don't know yet if the sensors are picking up the cam. May have to adjust the sensitivity..The problem is when driving around the truck throws P0171,P0174, and P0300 SES codes and the LTFT's will show 25% at idle and around 15% under load. I thought initailly I had a vacuum leak or air leak and I tore the truck back down from the CAI to the TB. My Vac/Boost Guage shows -18" and I still have idle RPM up in the 800 RPM range until I solve this. I added a GSS341 Walbro a few weeks prior to the injector/head/cam swap. I run Pacesetter LT's, no cats and a Magnaflow. I also run a water/meth kit until I get an intercooler built for the Vortech. I also run a 2600 stall.

Any suggestions on why the LTFT's are all out of sorts. What would cause them to change from idle to mid-rpm and then back at idle.....

I am attaching tune and log. Be easy. This was my first tune in a motel while the head and cam was being installed. I was guessing at most of this and was actually surprised when the truck fire and idled in as smooth as it did with the cam and heads....

I'm not 100% familiar with those trucks.....
is there a MAF sensor on them>and more imprtantly is it on yours??
are you in Speed density or running normal..
if you are using the MAF then you need to disable the MAF to tune your VE
and after the VE is in line then you can go to tuning the MAF table to match as well..
I highly suggest looking at it with a wideband in an o2 bung as it can tell you a lot more than LTFT's especially if the vehicle is modded

you definately need to add some fuel to your VE table and MAF table after you have changed cams...
but its not a blanket amount..usually down low you need to lean it out..so a blanket amount of increase would cause it to stumble at ilde cause of too much fuel..
p0300 is common with cams and most people just disable the code...no big deal...
also most cammed cars idle and drive in teh same areas..
and Idle trims you realy need to take with a grain of salt as there is he issue of overlap causing false readings
you can also always filter out things by driving only by not allowing any FTC's that fall into the idle category toplot in the histo...

[FlaBouy]

Yes I am still running the MAF. It is at the CAI. I moved the IAT sensor from that position to 6" prior to the TB. I now read correct charge air temps coming off the S/C. I spray my meth about 8" prior to the IAT sensor also. I just installed the bung and LC-1 O2 sensor at lunch. I unhooked the MAF on Saturday to tune the VE but after about 10 seconds the truck would not run. It just stumbled and died. I rehooked the MAF up and tried to manual change VE table based on my last log but it made the situation worse. At idle it shows +25% LTFT and negative single digit STFT's. Once i reach speed the LTFT's move to about +12-15%. I just thought it was weird to see the LTFT's cycle like that. Once back at idle they go to 25%. My main concern in all of this (other than seeing the LTFT's dance) is the P0171 and P0174 codes. They sort of justify what I am seeing with the LTFT's. They only throw at idle or coming down to idle off throttle... That why I thought I was getting air in the mix somewhere, under vacuum it was pulling from somewhere the MAF didn't register.

Any suggestions on how to disconnect the MAF without killing the motor? Should I be turning anything off in the software along with pulling the plug?

Thanks for your input....

[EC_Tune]

You don't "necessarily" need to unplug the MAF, just set the MAF fail frequency to 0 Hz and the P0103 DTC to set on the first failure instance.

[Zick]

I just scanned my truck yesterday for the hell of it and noticed this same problem. I did a full VE tune via WB about a month ago and it was dam near perfect and even tuned the MAF too. Now all of a sudden my LTFT are also about +20-25%.

The log for 2-27 is from yesterday running normally. Lots of + LTFTs.
The log for 2-28 is in the SD tune so you can see that my AFR% error is not that far off.

[FlaBouy]

So Zick, under your MAF log I noticed your fuel trims are basically behaving like mine. Are you telling me this would be normal? Here is a wot log just prior to the head/cam/inj install. Notice the fuel trims... So much tighter... Although inj duty cycles were 120% I had pretty good control of most everything else..... I had just installed the walbro 255lph pump at this point preparing for the injectors. BTW could someone look at the injector scaling in my tune and verify those. I believe I scaled those Siemens 60 LB to a fuel rail pressure of 58 lbs. I notice yesterday with the new injectors installed my pressure guage actually reads 54 lbs. I have the 04 returnless fuel system. Maybe a fuel voltage booster is in my future....

Thanks guys for your time.....

[Zick]

I only know enough to get me in trouble.

I can't say for sure if this is normal but I don't recall seeing it act this way before. Hopefully someone else more knowledgeable will chime it and let us know.

[FlaBouy]

I only know enough to get me in trouble.

I can't say for sure if this is normal but I don't recall seeing it act this way before. Hopefully someone else more knowledgeable will chime it and let us know.

I hear ya.. Don't feel like you are stroking that boat alone...

I think my issues are in the VE but my inept abilities to tune have only made the issue worse when I try to fix it. So I put the posted tune back in it, drive around with my flashers on and 4 plug wires undone until I get time to do some more tuning on this daily driver.....

Hehe, I am thinking of going back to a modified stock tune and working from there out. This tune has been modified a lot over the last 6 months as the truck grew in mods....

[Zick]

Well after a little VE tuning, here is a log done with everything set back to normal except for enabling the MAF. I just left the MAF freq set to 0.

Everything looks good except that I forgot that when I have the MAF disabled it reverts back to the low octane table. I couldn't figure out at first why the truck felt sluggish and my timing was so low.

[WS6FirebirdTA00]

I forgot that when I have the MAF disabled it reverts back to the low octane table. I couldn't figure out at first why the truck felt sluggish and my timing was so low.

i think thats happened to us all some point in time haha

[FlaBouy]

Thanks for your effort Zick. I disabled MAF last night and started retuning VE. Made major improvements to LTFT's last night. Table still a little choppy in areas but further refinement will take care of that.

Hehe on the the High/Low Octane timing table issue. Mine are one and the same since I went to a supercharger....

Thanks for your input....

[Zick]

FlaBouy,
Hows it coming along, did you ever get your LTFTs in-line?

I did a retune of my VE table and got my LTFT all within 1-3% and it was fine with all the tables back to normal except for the MAF, but as soon as I put the MAF setting back it, my LTFTs starting doing the exact same thing again. They were like 20+ at idle and only dropped down to about 12-15+ while driving, then they go back up again when stopping.
This is driving me nuts, what the hell am I doing wrong.

FYI: I did recalibrate my MAF once before, but I may just put it back to stock since this seems to have started after doing that but I'm not 100% sure.

[WS6FirebirdTA00]

redo the MAF again, if the VE was off when you recalibrated it it could screw with things, I have never recaled a MAF though lol

[Zick]

Thanks WS6, I think I'm going to just set the MAF back to stock and then try and re-scale it again.

So if you've never rescalled your MAF, how are your LTFTs? If they are within check, how did you get them to stay down with the MAF or are you not using a MAF?

[WS6FirebirdTA00]

im running OLSD

[Zick]

Gotcha

[FlaBouy]

Zick

Yeah I got the LTFT's back to within 2%. Haven't brought the MAF back online yet. Just got my new USB cable back and installed with the LC-1. Having a problem with the resolution on the LC-1. It bounces around like crazy. I will probably be putting my MAF back online the next day or so. Anything I should look out for when I rescale the MAF? I haven't done a MAF rescale before so I need to read up on it...Need to do this quickly since I am running around with a 650HP blown Avalanche that's not adding fuel under boost.... Can you say...Drive the speed limit!!!!!

[Zick]

Zick

Yeah I got the LTFT's back to within 2%. Haven't brought the MAF back online yet. Just got my new USB cable back and installed with the LC-1. Having a problem with the resolution on the LC-1. It bounces around like crazy. I will probably be putting my MAF back online the next day or so. Anything I should look out for when I rescale the MAF? I haven't done a MAF rescale before so I need to read up on it...Need to do this quickly since I am running around with a 650HP blown Avalanche that's not adding fuel under boost.... Can you say...Drive the speed limit!!!!!

lol

No for the most part, scalling the MAF was fairly easy except that I believe my problem was that my VE wasn't fully tuned when I did it so it threw off the MAF scale.
How bad is LC1 fluxuating? Is jumping by points?
My moves around a little but its only by .3-.6
Good luck and let me know how it goes.

[FlaBouy]

lol

No for the most part, scalling the MAF was fairly easy except that I believe my problem was that my VE wasn't fully tuned when I did it so it threw off the MAF scale.
How bad is LC1 fluxuating? Is jumping by points?
My moves around a little but its only by .3-.6
Good luck and let me know how it goes.

Not too bad but it is driving me crazy. The bad thing is it came with a DIYTune gauge and the gauge will only read 000. The analog input to the interface looks good though. Here is a log of the FT's prior to turning on the MAF tonight, as well as what the MAF did to the FT's on the next log. Second log is ugly with the MAF on. I now have to figure out how to scale the MAF to get the FT's back in line. I will post up once I get it figured out. If anyone has scaled a MAF and feels like jumping in, just let me know....

[Zick]

Whoa, what is going on with your IATs. One min its like 140* and the next its 95* and then back and forth. How the hell does it drop in temp so fast?
Is that just from your SC?