Check your fuel system first. 
PLEASE HELP. Expert Tuners Needed
PLEASE HELP. Expert Tuners Needed I have a 408 setup, BBK intake, 42# injectors, long tubes, ported 241 heads, .020 milled, etc etc. Makes 442/439 on dynojet.
Recently, I started getting a miss at 4000+ rpm in 2nd. It still pulls, but it seems power is going in and out, sometimes almost "spitting". I ran a log and did not see anything out of the ordinary. I did notice my fuel pressure drop to 50psi during the 2nd gear run. Is that normal? Here is a link to the HP Tuners log file. Any help would be greatly appreciated.
My Log File
Recently, I started getting a miss at 4000+ rpm in 2nd. It still pulls, but it seems power is going in and out, sometimes almost "spitting". I ran a log and did not see anything out of the ordinary. I did notice my fuel pressure drop to 50psi during the 2nd gear run. Is that normal? Here is a link to the HP Tuners log file. Any help would be greatly appreciated.
My Log File
I can check those tomorrow. Can others chime in as well on fuel pressure dropping to 50psi during WOT? I have a 255lph pump in the tank. Is this enough to support 42# injectors running 65-72% duty cycle on a 408? Also of note, I replaced the TR55 with TR6's tonight. Can't say they helped yet as I had a few beers installing them and won't get to test it until tomorrow 
The pump should be able to support you motor. The question may be can the factory wiring/power supply support your fuel pump? I know Racetronix sells what they call a hot wire kit.
I bought one of those upgrade kits. It seems to work fine until recently. Interestingly, I installed the new TR6 plugs last night and the problem seems to have gone away...
Except for the fuel pressure drop.
Thanks
Except for the fuel pressure drop.
Thanks
Last edited by 5ltrBetr; May 23, 2007 at 01:47 PM.
Well, sad to say that my problem has returned. 
Installed the TR6's and all seemed fine until today, it started "spitting" back, fluctuating power, at 4000+ RPM. I don't get it. I have checked plugs, wires, fuel (seems OK excpept the pressure drops to 50-55PSI at WOT). Does anyone suspect a mechanical failure? The lifters are new LS7 units, the rockers are stock, the pushrods are chrome molly, the spings are comp 918's. I am feeling the frustration mount... I have HP Tuners. Is there anything in particular I should be monitoring while doing a 2nd gear run? Aso, the O2 sensors are less than 6 months old.
Thanks in advance!
Installed the TR6's and all seemed fine until today, it started "spitting" back, fluctuating power, at 4000+ RPM. I don't get it. I have checked plugs, wires, fuel (seems OK excpept the pressure drops to 50-55PSI at WOT). Does anyone suspect a mechanical failure? The lifters are new LS7 units, the rockers are stock, the pushrods are chrome molly, the spings are comp 918's. I am feeling the frustration mount... I have HP Tuners. Is there anything in particular I should be monitoring while doing a 2nd gear run? Aso, the O2 sensors are less than 6 months old.Thanks in advance!
Last edited by 5ltrBetr; May 24, 2007 at 01:30 PM.
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Verdad Gallardo Here is a pic of my log file during the 2nd gear run where is is "breaking" up after 4000 rpm.
Log File Pic
Log File Pic
your LTFTs are locked crazy *** high, 24-25%... do you have another MAF you could try or one you could borrow and try (though this is just ruling out since the NB O2s stay relatively high? Do you have a code set?
I am kind of new at the tuning gig, what are the LTFT's? I have suspected the MAS since at the same time I feel the dips in power, there are corresponding dips in the MAS readings. I don't have any codes set since I have deleted most of the ones in question. Maybe I should re-enable those and get the ones that are being set.
Holy Yikes! I should figure out why. Any ideas of where to start looking? MAS I assume would be a starting point. Where else could I get a command for that much fuel? That would explain the 10PSI drop in fuel pressure at WOT as well.
I just thought of something... One change that I did make was I remounted where my exhaust clamps are positioned to give more ground cleareance. As a result, under full acceleration, the clamps bang the bottom of the chassis a bit. Could the computer be sensing detonation because of that and pulling timing/adding fuel??? I also added a catch can setup for my PVC system. I'll post some pics of that tonight. Just a thought.
I just thought of something... One change that I did make was I remounted where my exhaust clamps are positioned to give more ground cleareance. As a result, under full acceleration, the clamps bang the bottom of the chassis a bit. Could the computer be sensing detonation because of that and pulling timing/adding fuel??? I also added a catch can setup for my PVC system. I'll post some pics of that tonight. Just a thought.
I checked everything and there does not appear to be a leak. I am in the process of cleaning the MAS now. I moved the clamps. I'll do another log run in a few minutes and report back...
Good greif. Nothing seems to change these things. I thought maybe my injector settings might be wrong. They are Bosch 24508208 injectors rated at 36lbs at 43.5psi. They are rated at 42lbs at 58psi. I changed the value to 62psi and then to 52psi with no change in LTFT behavior. I wish I knew more about tuning... I also wish I had an old log. I'll search some more...
Am I on the right track here? I read something about porting the MAS causing high LTFT's. I increased my MAS Table by 20% across the board and the LTFT's came down to 21%. Interestingly, my injector duty cycle went from 72% to 91%. Why? Am I on the right path here? Thanks!