2015 gm lv3 4.3 runs rich with maf sensor plugged in, high fuel rail pressure
2015 gm lv3 4.3 runs rich with maf sensor plugged in, high fuel rail pressure
need help: i have a 2015 lv3 4.3 that came out of a 2015 1500 truck, factory ecm present but has had the program calibrations reflashed to remove and disable active fuel managment operation, vats ect. current is installed in a rock crawler chassie, my question is , with the maf sensor plugged in the engine starts , fuel rail pressure is 650 ish and after a moment fuel rail pressure goes above 1600 to 2000 psi fuel trims ltft's go to the far negative vehicle starts loading up to the point of fouling spark plugs, only dtcs im getting at times are p0101 maf performance, when i unplug the maf the engine dies as i would expect and with maf sensor unplugged when i start the vehicle again frp pressure is as i would expect at around 650 ish and ltft and stft are right around plus or minus 5% so corrcted they are close to 0, the engine will run fine this way if i leave the maf unplugged, if while running i can plug the maf back in and the engine will continue to run ok until i shut it off and restart then im back to high fuel trims all over again, i have worked over the phone with the tuner and they are unsure of the problem we have tried a second ecm with a mirror tune and tried a second factory maf sensor and no luck so im reaching out to the pros on here hopefully can point me in another direction, and advised me on what calibration point i should try to focus my attention on or if anyone on here has had a similar case thanks in advance wayne also to add i have verifed batt power 5 volt ref. and ground as well as signal and signal ref crkts from ecm to maf sensor connector are good, also i get the expected crkt dtcs you would expect to see with maf sensor unplugged wich would tell me that the ecm is able to see the crkts in question hope my explanation makes sense to somebody on here
can you post up a tune with the current settings that you are running? Also, get a scan of what it is doing with the maf plugged in and let us see what its doing when the pressure goes up.
i can do that thanks for your reply i wont be back in front of the car till this next week but i will grab some recordings and upload them as well as the tune do have any specific tuning maps you would like me to pull down and upload? or the entire file? im new to this posting so im trying to figure it out thanks
here is the tune as it is set up from the original tuner attached, along with a scan of the maf fault present as well as when the engine is running ok hope that i have posted it properly let me know i will be back in front of the vehicle on wed. and can collect some diffent data or whatever else may be helpful thanks for the assistance
motor is stock 2015 4.3 all hardware , ecm are stock 2015 components only thing i know for sure at this point is the AFM Active Fuel Management has been tuned out/disabled by the original tuner shop, MAF sensor is stock plumbed into custom tubing with ample distance between inlet and outlet sides with no sharp bends or transitions between air filter and throttle body, i dont feel at this point that i have an injector fault due to how well the engine runs when the MAF sensor is unplugged and in density, LTFT are close to where i would expect to see them at idle which is where it is loading up with the MAF plugged in, application does have an aftermarket fuel supply pump but i have 65psi supply pressure to the high pressure pump, im not sure at this point that it is tuning why i reached out to some of you guys in hopes that maybe someone has seen this or it makes sense, original tuner says they have not had this problem and they are unsure where the fault may lie, so i am in the diagnostic mode at this time
that is what i am trying to figure out i have been playing phone tag with him and it is not helping the proc/s ess but i am leaning toward there being something with the MAF calibrations im going to try and get some data logged specifically the MAF stuff tonight anything in particular you might say i should look at besides voltages gm/s, hrtz. ect, im new to the tuning side of things i copied the vertical and row axis cell mumbers from the vcm editor and created a historgram in the scanner but i havent taken any recordings yet hope i described that right, am i right in saying that the gm/s at MAF sensor should be roughly proportional to liters or roughly 4.3 gm/s at hot idle for this motor
Last edited by wayne sanchez; 07-18-2018 at 05:42 PM.
not for maf no, just make sure you log maf freq and airflow - just make a histogram mimicking the maf airflow chart in the editor plotting ltft - if you want subtract 40% (multiply .6 the whole chart) of fueling (since that's where your ltft are pegged at) from the maf chart from 4khz on down and see if the trims settle better
but if your going to tune maf - put it in maf only mode - dynamic airflow - high rpm disable 200rpm / re enable 100
so im finally going to be getting back in front of this car and going to try and get the maf tuned i will advise as i get some info and hopefully can get it figured out
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