HELP AGAIN!!!! (awd launch related)

[1fast97gsx]

This is a repost from the extreme tech section where nobody could help me out so maybe you guys can...

Help with wierd launch!!!

So everytime I launch my car it takes off fine until around 6k rpm and then the car starts sputtering / jerking really hard. I'm not sure what this could be, but it was doing this last year as well. This happens even if I'm only running 14 psi or 25 psi .. it always happens. I have since then replaced the engine, trans, turbo, intercooler, injectors, plugs, wires, coilpacks, ignition module and so on. What's left really besides the ECU causing this problem? I only have a problem like this during a hard launch and only in 1st gear. I'm totally stumped herem but I want to take this car to the track!!! What about a bad ground on the fuel pump?

 

[tsi_punk]

are you dumping or slipping the clutch?

 

[92awddsm]

How much fuel do you have in the tank when this happens? Does it do it on a full tank? Reason I ask is maybe you are launching hard enough on low fuel that you actually uncover the fuel pickup and causing a lean condition at the top of first gear. Have you logged during this problem? Any knock or crazy o2 reading while this is happening? Thats the only thing I can think of if it only does it during a hard launch.

 

[1fast97gsx]

are you dumping or slipping the clutch?

Slipping ... I luanched really good all last summer ( low 1.7s ) but at the end 1 day it started doing it. It does it at full tank or 1/4 tank .. makes no difference. I wanted to do a datalog, but the one night I decided to do it my logger wouldn't connect with the ecu for some odd reason. Then the logger started working again .. but I'm afraid to even try launching it because it jerks REALLY bad...

 

[1fast97gsx]

How much fuel do you have in the tank when this happens? Does it do it on a full tank? Reason I ask is maybe you are launching hard enough on low fuel that you actually uncover the fuel pickup and causing a lean condition at the top of first gear. Have you logged during this problem? Any knock or crazy o2 reading while this is happening? Thats the only thing I can think of if it only does it during a hard launch.

the fuel thing interests me .. I was also thinking something like that or maybe a bad ground on the fuel pump. However if it's either of those things it would do it towards redline in higher gears as well right? Car runs great once I'm out of 1st gear.

 

[1fast97gsx]

I have the fp rewire done as well ... a broken relay would keep the car from starting period right?

 

[sonicnofadz]

I am definitely not a 2g expert by any means, but it sounds like you may be hitting fuel cut.

 

[1fast97gsx]

I considered that as well ... however it does it dialed in at only 14 psi as well. I did probably 50 passes at the track last year and had no problems ever with fuel cut ... then 1 day this started happening. ( without me changing anything on the car ) Plus it only happens during a hard launch and not in any other gears no matter what level the boost is at.

 

[DSMKevan]

It could still be fuel cut. I was hitting it in 3rd gear 4500 rpm 65mph...every time. I was only boosting 15lbs, and I have a 190 pump installed as well. I dunno though, Im a 1g guy

 

[1fast97gsx]

well I've tried everything ... adjusted the safc both ways, messed with the mas screw, messed with the boost .. still does it. Any other ideas?

 

[sweet97]

What about the obvious and not having enough fuel under hard launch for the pump to pick-up? Ty a ful tank.

 

[98TsiAWD]

LTFT's set properly? What is your a/f at 6k?

 

[1fast97gsx]

help the problem is back!!! I got rid of it for a while with a new cam angle sensor but after a few launches it started again. What about a misadjusted tps? ltft are close to perfect. On a 3rd gear pull my timing has a nice upwards curve and hits 20 degrees at 7300 rpm.

 

[1fast97gsx]

LTFT's set properly? What is your a/f at 6k?

according to the logger I'm at .94 volts or so ... the capture rate is too small to let me do a lot of scrolling around just from doing a launch, but the O2s are a pretty flat line on the pic.