Car was tuned last year with a stock map sensor on uberdata and ran fine. Brought it back out this spring and it would run good except when you let off the throttle at high rpm it would get a surge of fuel so bad the motor would usually stall, or at least let out a huge cloud of smoke or giant fireball out of the exhaust. Figured it must be a tuning issues even though it did not do it last year. Switched to crome and a 3 bar map sensor. Tuned everything and it still does it, afr will be 11.5 to 12 all of the way up in boost but as soon as you let off you still get this surge of fuel that usually floods the motor that you can instantly smell. I completely leaned out the vaccuum columns to where the injectors pretty much shut off in half of the vaccuum map in the higher rpms but this did not fix the problem, just made it impossible to drive on the interstate. I even tried running it up to redline at close to 0psi and it still flooded, it something with higher rpms. Definately does not seem to be a engine management problem as it has done it on two totally different tunes and systems, and the original uberdata tune did run properly before.

setup is

lsvtec with 60-1
precision 880cc injectors
gm 3 bar map sensor
walboro 255
aem fpr
70mm jg throttle body

I am thinking mabe something with the FPR but I wondered if anybody else has had this happen before. Pretty much all these parts are still pretty new and only have a few hundred miles on them.

 

when you close the throttle the injectors shut off, well supposed too. appearently not in your case.

most likely your TPS sensor is out of adjustment and the computer thinks the throttle is open when it is not.


which could throw off your entire tune i would imagine. i would start there.

 

Bump! because I have almost the same problem, just not during decelaration. It's happening during my startup. I also have 880cc, 3bar, and a walbro 255 fuel pump as well. Strange?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by agrn93ls &raquo;</TD></TR><TR><TD CLASS="quote">when you close the throttle the injectors shut off, well supposed too. appearently not in your case.

most likely your TPS sensor is out of adjustment and the computer thinks the throttle is open when it is not.


which could throw off your entire tune i would imagine. i would start there.</TD></TR></TABLE>

That is what I guessed at first too, since it is an aftermarket TB. During normal driving under deacell I see the injectors turn off, the wideband maxes out lean. But just to be sure I checked the voltage at idle and it was a little high at .55v. Its not adjustable so I wired in some pull down resistors and got it all the way down to .4v. But all that did was make the throttle way too touchy because the injectors would not turn on soon enough then. It still flooded on deacell even with the TPS setup that way.

 

maybe a leaky injector?