Chesk

Hey guys...
any idea why such a bad mpg?
I have a lm7 5.3 2006 4l60e 3.73 rear end, 225-75-15 tires, swap on a 54 chevy truck,
It's been a year since I finished the swap and drove very little, but I recently did a 300 mile trip and got 13 mpg driving 60 mi/h at 1900rpm most of the time.
my torque pro app shows me 20mpg but my mileage x fuel consumption calculation shows 13mpg
my torque app also shows the ltft both banks between +17 and +25
the torque app shows the fuel with 39% ethanol, could it be my fuel?
another detail that I noticed today is that if I disconnect the maf the ltft decreases a lot, it oscillates between 0 and +8
when I'm accelerating to gain speed it's at zero or close to zero, but when I stop accelerating the ltft goes up to +8
I have a new corvette style pressure regulator and walbro 255 in tank , constant pressure at 58psi
sparks new oem
I changed the intake gasket
I didn't find any vacuum leaks in the engine.
I have a cone model air filter.
can the high ltft be influencing the high fuel consumption?
I have no experience with these engines, what else could I do to find the fuel consumption problem?

Chesk

what else should i look for in torque pro? how to use it to find my problem?

rpturbo

iTrader: (47)

What are you using to get the accurate mileage? Has this been tuned since it was swapped? There just isn't enough information here to really start, but you definitely have to start with why the ltfts are so far off. You either need a tune because it's way off, or you possibly have a exhaust leak before the O2 sensors, causing it to add a bunch of fuel, which, well would give you garbage mpgs.
As far as the app goes, I have no clue, I don't use it, I use HP Tuners.

78TranzAm

If you haven't had the swap tuned. It won't run the best it can in any way. Even if its stock. It still needs to be tuned.

Chesk

-I'm using a gps app for the mileage
- not tuned, disabled emisions, vats, but not tuned
the torque pro app is showing 39% ethanol in the fuel, could the 2006 tahoe use this fuel?
- I've looked for leaks and vacuum and haven't found anything suspicious
that if I disconnect the maf the ltft decreases a lot, it oscillates between 0 and +8
when I'm accelerating to gain speed it's at zero or close to zero, but when I stop accelerating the ltft goes up to +8
what information do i need to provide?

Chesk

pcm has been disabled emissions, vats, electric fan enabled but not tuned
the torque app shows the fuel with 39% ethanol, could it be my fuel?
another detail that I noticed today is that if I disconnect the maf the ltft decreases a lot, it oscillates between 0 and +8
when I'm accelerating to gain speed it's at zero or close to zero, but when I stop accelerating the ltft goes up to +8

LLLosingit

iTrader: (4)

Tune will help, Running a 3.73 gear with that tire isn't helping either, Go to a taller tire or change the gear if you're doing a lot of highway driving. My Silverado is much heavier and get's 15mpg in town and 18 on the highway but it also only turns 1650rpms at 65mph.

aknovaman

iTrader: (7)

Is the PCM from the same donor engine? Possible that pcm file is set for regular gas injectors and you have flex fuel injectors? Flex are 33lb and regular are generally 25lb. If the injector connectors are square, they are flex; if rectangular they are normal injectors. Other than that you heed HPT to read file and datalog too see whats going on.

Chesk

[QUOTE=aknovaman;20443184]O PCM é do mesmo mecanismo doador? É possível que o arquivo pcm esteja definido para injetores de gás regulares e você tenha injetores de combustível flex? Flex são 33 lb e regulares são geralmente 25 lb. Se os conectores dos injetores forem quadrados, eles são flexíveis; se retangulares são injetores normais. Além disso, você presta atenção ao HPT para ler o arquivo e o registro de dados e também ver o que está acontecendo.[/QUOTE
]- yes the engine, trans, pcm, injectors, all sensors came out of a 2006 tahoe
- I imported this complete swap engine to Paraguay, maybe it's the fuel from here that is giving problems?
with the maf disconnected i got 16mpg on a short ride driving 55 to 60mph at 1600 to 1900 rpm and the ltft goes down from +15 to +24
for +4 to +10
- I don't have access to hpt
only obd2 and torque pro

aknovaman

iTrader: (7)

Is arrow on MAF pointed in airflow direction (toward engine) ? Has engine been sitting for a while not running? Injectors may be sticking and not flowing correct amount which the O2 sensors detect, adjust the injector open time and mess up AFR.

Che70velle

iTrader: (6)

To everything, TUNE, TUNE, TUNE..
You see what I did there, right?
All kidding aside, invest in a good tune, and let the tuner know that your looking for mileage. He/she will lean it out at cruise and your mileage will go up decently.

Chesk

-yes, the maf arrow is pointing to the engine.
-Yes, the engine was stopped for about 5 or 6 months.
- a friend cleaned the injectors 2 times, but we had no references to know if they were flowing well, but they all flowed an equal amount of fuel in the test.
- here in paraguay there is no one who can make adjustments to my pcm, I will try at the chevrolet representative but I don't think they know how to make the adjustments I need

Chesk

yes, this is the way, but here in Paraguay I still haven't found someone who can tune this engine, these engines practically don't exist here, I'll try in the chevrolet representative, but without hope.
I'm willing to buy a hptuner but then another problem I won't know about tune

Che70velle

iTrader: (6)

If you can get HPTuners, and a laptop, you can log certain run files, and easily email the file to a tuner here in the states. We can read data from the files you have logged, and make the necessary changes. The file is then emailed back to you, and you install new tune into the HPTuners program. It’s incredibly simple.
Buy the HPTuners Pro, the unit allows for a wideband gauge to be utilized, which will help in optimizing the AFR’s in order for the MPG’s to be maximized safely. If you need help finding a good tuner here, send me a PM.

aknovaman

iTrader: (7)

I dont see how lean cruising the file fix his LTFT problem

Che70velle

iTrader: (6)

It won’t. But a tune for mileage will help his MPG issue. I’m not going to pretend that I’m a tuner, as I’m a newb in that dept.
I’d want to see what HPTuners says the LTFT’s are VS. the Torque APP since LTFT’s feed off the STFT’s. Could be something mechanical here also, if the Torque APP is remotely accurate.

Chesk

I also doubted the accuracy of the torque app but I connected it to another new car I have and the ltft works at zero, so it means that the lm7 5.3 is having some problem really

68Formula

If the 8th digit in the VIN is "Z", then it'd be an L59 (Flex-Fuel) 5.3L, not an LM7. Are you sure it's an LM7?

aknovaman

iTrader: (7)

The data spit out of the PCM does not change based upon the scan tool.

Chesk

I couldn't find the vin in the engine, but the purchase invoice shows a vin with the 8th digit T