2011 gmc 6.2 /4l80e help

[laurieandmike]

hi all
my dad has a 57 belair with a 2011 6.2 /4l80e
e38
t42
dod is disabled
vvt is zeroed out
car seems to idle great but falls flat on its face under load
i tried with maf pluged in and not pluged in no real difference
ltft seems to go +25% out of no where
please help

[edcmat-l1]

Post the tune file.

Put a fuel pressure gauge on it. One you can tape to the windshield so you can watch it while you drive.

[laurieandmike]

fuel pressure stays at about 60psi

[laurieandmike]

vvttune1.hpt

[edcmat-l1]

fuel pressure stays at about 60psi

That's what everyone says and around here it's code for 'I haven't really checked it, I'm assuming'. Your MAF table is already doubled. Granted they do need recalibrating when you move them like in a swap vehicle, but with it being doubled I'd suspect low fuel pressure.

You aren't logging MAF Hz or injector on time. Both are need for diagnosis and tuning.

Also, about halfway through your scan you lose RPM. Looks like it was still running so must be a scanner glitch.

[laurieandmike]

thanks for reply
i keep checking fuel pressure but will take a video
maf was bought new but i am not a tuner by no means lol
how do i add channels like hz or injector
yes rpm justed stoped
the speed moves even in park
thanks again for the info

[edcmat-l1]

thanks for reply
i keep checking fuel pressure but will take a video
maf was bought new but i am not a tuner by no means lol
how do i add channels like hz or injector
yes rpm justed stoped
the speed moves even in park
thanks again for the info

If the speed moves in park you got issues LOL

Post a picture of the cold air intake and MAF location.

[laurieandmike]

will get a pic
will also see if the vss/iss is pluged in backwards or not

[Alvin]

This is dead lean any time you are getting on it.

This also sounds like ISS / VSS are crossed.

could be also.. if the VSS wires aren't a twisted pair. VSS will read noise otherwise.

[laurieandmike]

Attachment 151669

[laurieandmike]

Attachment 151670dad4.hpl

[laurieandmike]

here is last scan
vss wires were backwards
still falls flat on its face under load

[Alvin]

Still very lean when you are getting on it.

[laurieandmike]

where should i go from here?
i am going to try to get the fuel pressure gauge setup so i can see it
no codes
thanks againfor reply

[edcmat-l1]

where should i go from here?
i am going to try to get the fuel pressure gauge setup so i can see it
no codes
thanks againfor reply

First step is checking and verifying that the fuel pressure is good at all times. Not just sitting still idling, but under power, moving, etc.

[2xLS1]

FP is the #1 issue I see in swaps. #2 is probably trying to run it with open exhaust close to the O2 sensors. But I just want to hear it run and start tuning it. Well finish the build first.

[edcmat-l1]

FP is the #1 issue I see in swaps. #2 is probably trying to run it with open exhaust close to the O2 sensors. But I just want to hear it run and start tuning it. Well finish the build first.

Yep and for me not just swaps it seems like everyone just ASSumes their vehicle has adequate fuel pressure. It's the "nah that ain't it" attitude.

[2xLS1]

OEMs go to a lot of trouble to engineer and manufacture robust fuel systems in their EFI vehicles. DIYers usually don't when it comes to a swap.

[edcmat-l1]

OEMs go to a lot of trouble to engineer and manufacture robust fuel systems in their EFI vehicles. DIYers usually don't when it comes to a swap.

I agree but that still leads to people ASSuming everything is fine fuel system wise.

Same thing applies to "all new parts" syndrome. "Fuel pressure is fine. It's a new pump, all new parts".

[blindsquirrel]

"I opened the hood with it running and looked at the GzYcsFocusqp* chrome polished billet aluminum gauge I keep screwed onto the fuel rail and it was somewhere right around where it's supposed to be, so pressure isn't the problem."

* Yes that is a real 'brand' name one of the Chinese drop-shippers uses on Amazon.