need help solving lean condition

[Scottydoggs]

im just going back to work, good old winter layoff, so sundays would be best.

 

[muncie21]

When you first start your motor, the PCM is in open loop mode, meaning LTFT/STFT are locked. Fueling is done via the MAF and VE tables in the PCM. Only when you hit operating temps do the fuel trims unlock and adjust according to your O2 value.

If you are getting bad gas mileage + your PCM thinks you are running lean, sounds like outside air is hitting your O2s. This will make your PCM think you're running lean, which compensates by adding more fuel (positive fuel trims). In reality, you're running rich because the additional oxygen isn't from the combustion process, it is outside air leaking in.

I would pull the plugs to see if they show lean or rich condition and troubleshoot from there.

 

[HACK BLOCK]

here's the pictures of the passenger side plugs. #8 plug was loose

 

[HACK BLOCK]

here's the pictures of the passenger side plugs. #8 plug was loose

 

[Scottydoggs]

yup, those look like its running lean.

see any missing manifold bolts? the back one likes to break off or just come loose and fall out. had both happen in the past.

the hoe i just got has that back pass side bolt broke or missing. ill fix that when i install my headers.

 

[HACK BLOCK]

I think I noticed 2 missing on the passenger side I wasn't sure

 

[BlueCollarTahoe]

so to check for proper numbers you need to record the ltft1 and ltft2 while driving?

 

[Scottydoggs]

scan bank one and two

 

[shoplizard]

Just out of curiosity, how does the vehicle run on the highway at WOT? What is the MAF reading and what are the LTFT readings on each bank at WOT (wide open throttle).Your MAF should be around 200 GPM (give or take 20). and both LTFT's should be near 0. If the MAF readings are very low and the LTFT's are high I would suspect you have a faulty MAF sensor, some do not respond to cleaning. Leaking intake gaskets show only a minor fault at high RPM usually imperceptible. Also, monitor your fuel pressure while driving at WOT, this may be tricky, so be careful and use good equipment, this could tell you a lot. If the fuel pressure drops below minimum specs, it could indicate a faulty fuel pump and/or a plugged filter. Some of the filters are part of the fuel pump assembly (2005 and up). Good luck.

 

[BlueCollarTahoe]

okay im getting the same MPG as Hackblock as we seen in another thread. now i want to get the recordings down right as theyre doing in here. what exactly at im looking for?

idle:
RPM
MAF
LTFT1
STFT1
LTF1
LTFt2


and when yall say under pressure what does that mean? driving on thje highway at 65 mph? up to operating temp? all the [particulars i listed above is whats needed to compare?

 

[HACK BLOCK]

Just out of curiosity, how does the vehicle run on the highway at WOT? What is the MAF reading and what are the LTFT readings on each bank at WOT (wide open throttle).Your MAF should be around 200 GPM (give or take 20). and both LTFT's should be near 0. If the MAF readings are very low and the LTFT's are high I would suspect you have a faulty MAF sensor, some do not respond to cleaning. Leaking intake gaskets show only a minor fault at high RPM usually imperceptible. Also, monitor your fuel pressure while driving at WOT, this may be tricky, so be careful and use good equipment, this could tell you a lot. If the fuel pressure drops below minimum specs, it could indicate a faulty fuel pump and/or a plugged filter. Some of the filters are part of the fuel pump assembly (2005 and up). Good luck.

I haven't checked my fuel pressure or at wot but I know the ltft get really high the more rpm I give it. at idle it's around 5% or less, at 800 rpm its over 10% and about 15%-20% at 2500 rpm. my maf measures lb/s so at idle its 0.01 and at 2500 its around 0.05 lb/s.

 

[HACK BLOCK]

and I have no hesitation when accelerating

 

[Scottydoggs]

maf reading dont mean a whole lot here.

if anything you want to read its hurtz then you know where in the maf cells its in vs rpm. nothing you can do with that info tho. unless you have a tuner and are tuning it. then you can run the wide band if you have one vs the maf, or the long term and or short term fuel trims, then you would be able to adjust the maf off that info to bring the ltft back in order.

at this point id think its something other then the tune, vac leak really comes to mind when you see it go so positive.

be best to do intake gaskets, those tend to fail, cause vac leaks. or clogged up injectors can make it run lean too.

and as far as wot goes, gm screwed the pooch on these trucks. pe mode (power enrichment mode) dont kick in till your 90% throttle or more, and get this, with a 60 second delay, then it will kick in. who the hell is wot for a full minute? you dont do that at the track for gods sake.

when i got my truck it was flat on acceleration, i dropped pe enable to 60% throttle and zero delay, then set its afr to 12.3, truck now jumps when you hammer it.

 

[Justin]

Your plugs do not indicate to me that you have fresh air hitting the O2 sensors. If you did, the plugs would be black, as the PCM would be improperly overcompensating and dumping excess fuel in. If I read it correctly, you're fairly close to "normal" trims at idle, but progressively raise as airflow increases. Sounds like a classic case of a bad MAF sensor. Cleaning helps in some instances, but many are just too far gone.

I would bet money that it is not a vacuum related leak (post TB), as those tend to be more aggressive at closed throttle and zero themselves out under heavy load.

It could also be a fuel pressure problem. One way to test would be to disconnect the MAF sensor and compare fuel trims. If they drop back to zero or negative (likely), then the MAF is the culprit. If they remain high, albeit lower than with the MAF, then more digging is needed.

If you've considered tuning, our scan cable tune process would give us some pretty detailed information regarding what is going on, far more detailed than you're going to get from a snapshot. We do have a rental option as well if you didn't want to go the full route of the tune.

 

[Justin]

and as far as wot goes, gm screwed the pooch on these trucks. pe mode (power enrichment mode) dont kick in till your 90% throttle or more, and get this, with a 60 second delay, then it will kick in. who the hell is wot for a full minute? you dont do that at the track for gods sake.

To be fair, the 60 second PE delay is only on 2500+ models and it definitely sucks. Most will hit cat converter protection mode after about 10 seconds though and then go overly rich.

 

[Scottydoggs]

not to fight with ya, but i got a hpt. i own a 05 LT tahoe and thats how its set, (was set) and your right, its lame as ****.

pe tuned, trans tuning and added timing, and a few other little odds and ends. woke the whole truck up. didnt even touch TM yet. im sure that would add more untapped power, but id really rather not tear the tranny up over a few more HP.

this trucks not for beating on really, (its all stock) i got a toy for that. just wanted it to run better and get out its own way when needed. as you know, stock tunes are lame. they leave a lot on the floor. all you need to do is pick it back up and use it lol

 

[Justin]

That would be strange, as all 250+ 2005 Tahoes we've tuned over the years have a 0.8 second PE delay from the factory. Shoot me your VIN and I'll pull up a factory CAL and see if there isn't something different with yours specifically. You have me curious.

 

[Scottydoggs]

i do have the tow package, trans cooler and deep pan. not a flex fuel set up.

Ive seen that 0.8 delay in other files, with 5,000 rpm needing to be met.

my vin is 1GNEK13T85J199755

wish i had saved my first read. im so used to using a DHP where one click and the whole file is back to stock, or right click and import the stock file for what ever your working on, and the joy of being able to see the stock data in the same window. there was no need to save and compare with the original file. damn learning curve right there lol

that being said, if im wrong about the delay time, dropping the throttle enable % and re setting the afr in pe mode made it wake up when you floor it. pretty sure i got the rpm to zero as well as the delay time now. wb reads 12.3 as soon as it hits 60% throttle. hpt scanner does f-ing rule dont it? dhp was lacking in that department but it was super simple to set up and read back lines of data.

 

[Justin]

i do have the tow package, trans cooler and deep pan. not a flex fuel set up.

Ive seen that 0.8 delay in other files, with 5,000 rpm needing to be met.

my vin is 1GNEK13T85J199755

wish i had saved my first read. im so used to using a DHP where one click and the whole file is back to stock, or right click and import the stock file for what ever your working on, and the joy of being able to see the stock data in the same window. there was no need to save and compare with the original file. damn learning curve right there lol

that being said, if im wrong about the delay time, dropping the throttle enable % and re setting the afr in pe mode made it wake up when you floor it. pretty sure i got the rpm to zero as well as the delay time now. wb reads 12.3 as soon as it hits 60% throttle. hpt scanner does f-ing rule dont it? dhp was lacking in that department but it was super simple to set up and read back lines of data.

We have been ardent EFILive users and supporters for 13 years now and one of the key benefits that I've seen is the flexibility of their scan tool is quite a bit above HPT and HPT is leaps and bounds above many others. Both software packages are extremely capable though and really end up being about individual preference these days.

You will need to download the EFILive V7.5 software to view, but attached is your factory calibration, latest version, from GM. If you ever need to reference, it will just be a matter of cross-referencing the two software packages. You'll likely find that EFILive has a few tables that HPTuners does not and vice versa. For instance, HPTuners was missing some key fan control parameters for a good 4 or 5 years, but got E38 de-soot parameters in ahead of EFILive.

 

[HACK BLOCK]

Your plugs do not indicate to me that you have fresh air hitting the O2 sensors. If you did, the plugs would be black, as the PCM would be improperly overcompensating and dumping excess fuel in. If I read it correctly, you're fairly close to "normal" trims at idle, but progressively raise as airflow increases. Sounds like a classic case of a bad MAF sensor. Cleaning helps in some instances, but many are just too far gone.

I would bet money that it is not a vacuum related leak (post TB), as those tend to be more aggressive at closed throttle and zero themselves out under heavy load.

It could also be a fuel pressure problem. One way to test would be to disconnect the MAF sensor and compare fuel trims. If they drop back to zero or negative (likely), then the MAF is the culprit. If they remain high, albeit lower than with the MAF, then more digging is needed.

If you've considered tuning, our scan cable tune process would give us some pretty detailed information regarding what is going on, far more detailed than you're going to get from a snapshot. We do have a rental option as well if you didn't want to go the full route of the tune.

I was thinking of a tune but I figured I had to get this problem out the way. I'm waiting to borrow a friend's fuel pressure gauge to see what's going on. if that's not the problem I might just take it somewhere. being partially disabled with no place to work on the truck has me limited