Car dies monmentarily when throttle is opened off idle

[Jiffy]

Hi guys
I have a 2003 Cobra drivetrain in my 2002 car, have just upgraded to a SBTB, SCT2600 MAF (IIRC) 80lb injectors, JLT hi-boost CAI, 2.3L whipple. The car is undergoing tuning at the moment, but the idle isn't transitioning into revs/power when the throttle is opened and we can't quite sort this issue out.

Does the TPS need to be reset/calibrated/something else when it (and the throttle body) is replaced?

What signal is the ECU waiting for to inject more fuel when the throttle is opened? The TPS, more airflow through the MAF, an increase in revs? A combination? Something else? Is there a setting my tuner should be looking for to change to correct this?

Thanks in advance....

 

[fishpick]

I'd guess this is simply a TPS / throttle angle calibration thing... one of the first logs your tuner will do / have you do / should do is a rev log where you will take the car from an idle (when the car is "warm") and then go to like 1500 and hold for 30 seconds, then repeat the same thing at 2000, 2500, 3000...
You will find that doing that first "from idle to 1500 and hold it there" is actually pretty hard - because you will overshoot then fall under - until you use your foot to "dial it in" - that will then translate into some critical data for the tuner to "map" the accelerator angle to the TB to the TPS...

 

[decipha]

uhh no, there is no tp mapping, every time u turn the key on the ecu sets the lowest throttle voltage it sees to a relative throttle voltage of 0 this is called RATCH

before you can dial in tip in fuel u need to dial in base fuel, get the fuel dialed so the fuel error is as near 0 as to u can get it

then dial in inferred load / pct_load / totldst / LWFM table, whichever name your tuning software calls it

tell your tuning pal to then set the max aircharge correction ARCANTCOR to 1.000 (note thats not the same scalar as ARCWOTCOR which is the wot correction)

if that doesnt fix it, tell your tuner to start swinging the manifold volume scalar around, if its a lean tip in reduce, if rich increase

if that doesnt do it, check the maf voltage on a tip in, it should be smooth and not jump around nor spike, if it does youll need to install a few screens on it to make it flow less turbulent

all the info u will ever need to know can be found here

http://www.efidynotuning.com

 

[Jiffy]

ok found the issue!!

It turned out to be the PPRV!! So, it was totally gummed up with crud (I have always run the car to almost empty) and the PPRV was sticking due to all the crud clogging it up. What would happen, was the car would start due to residual fuel pressure in the rail, then the fuel pressure would erode as the idling engine consumed it, and the ECU would command more voltage to the pumps to raise the fuel pressure. The valve would be stuck closed, the fuel pressure behind the PPRV would build and build until it was reaching around 130PSI and the valve would open, the pumps are running flat out and LOADS of pressure hits the fuel rail, the FRPS would say "WHOA!", the pumps would close down, the PPRV would close, the fuel pressure was trapped in the rail, and the 60lb injectors couldn't open far enough to allow the revs to build because there was too much pressure behind them, then as it reduced down as it was consumed at idle the FRPS would command 'more fuel" and off we'd go again!

Pulled the tank, checked the PPRV, found it clogged with shit, cleaned it out and VIOLA!! 575rwhp at 14lbs with a 2.3L G2 Whipple (3inch upper), JLT Ram Air, Accufab SBTB. Thank **** for that....