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4.8 Idles but dies if you give it any gas

Old 12-30-2018, 01:11 AM
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Default 4.8 Idles but dies if you give it any gas

To start off hereís an outline of my setup:
stock bottom 4.8
228/230 cam
howards valve springs
gt45 turbo
decapped truck injectors
stock rails/fpr
walbro 450
5 speed
3 bar SD no o2ís

i just got the swap started for the first time a few days ago, tuning myself with hp tuners and the help of a buddy who has a lot of experience.
so far, the truck will start most of the time and Iíve got it idling decent around 900-1000rpms. Sometimes it doesnít want to start and will just fire and die, and when it does start and idle good, it will sputter if I give it gas and die around 1600-1700rpms will not rev past this. Im not an expert, but I tried increasing the ve table to give it more fuel as well as decreasing it to take some away, and it didnít seem to get any better in either direction. I also tried loading one of denmahís 4.8 tunes with almost the same exact setup as me and it still dies as soon as I give it any throttle which leads me to believe that the problem doesnít lie in the tune. Iím wondering what could be causing this and where I should look first? Does this sound like a fuel problem or possibly an ignition problem? The other thing is that my wideband is not getting a reading from my motor. With key on engine off it reads 18.7 full lean, when I spray some ether up the downpipe it reads 10 and slowly rises back to 18.7 as it dries up so I know itís working, but when my motor starts it shows loading and wonít give a reading so I have no idea where Iím at, is it possible the motor is running lower than 9 or higher than 19 and not registering on the guage? Commanded afr is right around 14.6 at idle and decreases as you give it gas. Thanks for the help guys!

Last edited by Evanniger; 12-30-2018 at 01:23 AM.
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Old 12-30-2018, 01:25 AM
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post your file and log
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Old 12-30-2018, 01:27 AM
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Originally Posted by Luke19901 View Post
post your file and log
Iím away from my computer, will post those files first thing in the morning
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Old 12-30-2018, 01:44 PM
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Here is a log I ran this morning as well as my tune file. As you'll see in the log i'm now having a hard time getting it to even idle, it is cold however about 40 degrees here in Ct and can't get it warmed up since it wont stay running, wont rev at all either. And as far as the tune goes, its pretty much a stock 4.8 manual tune flashed to a 3 bar and the ve table i interpolated up to 3 bar just to have something to start with. Other than that I have disabled vats, switched to speed density and put my injector flow rate in. Im going to grab my fuel pressure gauge from a friend who's borrowing it and double check that I have good pressure shortly.
Attached Files
File Type: hpl
1995 F250 4.8 Log.hpl (105.4 KB, 3 views)
File Type: hpt
F250 4.8 Tune.hpt (231.5 KB, 3 views)
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Old 12-31-2018, 06:52 PM
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So I checked fuel pressure this morning and had 10 psi. Pulled tank and pickup tube was leaking so I replaced it and now have 60 psi at key on and at idle, canít look at the guage while I rev it but guessing itís holding the 60psi. Truck runs worlds better, is reading on my wideband gauge now, and with the tune from sloppy mechanics slightly modified idling around 14.6 afr. Still canít rev past about 1800rpms tho. Itís like the truck hits a wall and just shuts off at that rpms, almost like thereís a governor or something. If I give it gas it will hit that spot shut off, recover at low rpms and then rev back to that spot and keep doing it over and over. Any ideas? Possible ignition problem?
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Old 01-01-2019, 09:02 AM
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drive train abuse in engine torque management is your problem.

but you have many other things that need correcting in that tune before you get started
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