sputtering only sometimes getting into boost at different throttle positions

Mods:
s16g-stock wastegate pressure
Evo yellow top injectors (510cc)
2g maf
jdm cyclone motor with working cyclone intake
3" exhaust turbo back
Alright so I picked 100/2000 a few weeks ago and have been battling this problem since day 1. When the car is still partially cold and not fully warm, it will run and boost nice and strong, but once its warm and I get on the throttle it'll buck and sputter like it wants to go and occasionally works its way out of it. I've replaced plugs and wires (magnacore wires-NGK plugs) with no change. I do have a stock fuel pump thats not re-wired along with a stock fpr, but I wouldn't think a stock FP would run out of juice at stock wastegate pressure (11 psi) on a small 16g.
I've done a boost leak test and there was one leak at the throttle body that I fixed with no change again. I'm pretty lost on where to go from here, and I guess if someone could tell me at what level the stock fuel pump would run out that'd be great.
Again I can drive it cold and it boosts perfect once warm it just bucks when getting on the throttle really at any amount. I've also grounded out the knock sensor to rule out timing being pulled from knock-no change.

 

[desant78]

How are you tuning this car? Or am I missing something here. Using a regular USDM ecu won't support the injectors. Stock injectors are 450cc.

 

Just a 2g maf to compensate for the bigger injectors for now.

 

[turbowop]

Just using a 2gMaf isn't enough to compensate for larger injectors of any size. It's close to 550's, but you still need to fine tune it with something like an SAFC since Maf's and injectors of the same size can still have variances. Even then, it's not an optimal way of tuning. This is likely where the problem lies.

 

I understand the need for a tune, I've run 2g mafs with 510 and 560 injectors before without issue. Was just seeing if someone had a similar issue which met the same criteria for when my problem occurs. Didn't know if maybe it ran better cold because the ECU gives the car more fuel, or if there is a sensor that could have gone bad once its warm. Just looking for ideas. Thanks for the help so far though, any and all help is appreciated. When does the stock fuel pump start to crap out though? I did check the spark plugs earlier after just replacing them a few days ago and the tips are white, indicating a lean condition so I thought perhaps the fuel pump may not be able to supply enough fuel when the bigger injectors are demanding it. And it being an intermittent problem suggests that maybe, its a voltage problem? Or perhaps something else?

 

[turbowop]

It could be any number of things, but you aren't really helping it by running injectors and air flow sensors that you can't properly compensate for. When is the last time the fuel filter was replaced?

 

[ktmrider]

Quoting GVR4LIFE:
I understand the need for a tune, I've run 2g mafs with 510 and 560 injectors before without issue. Was just seeing if someone had a similar issue which met the same criteria for when my problem occurs. Didn't know if maybe it ran better cold because the ECU gives the car more fuel, or if there is a sensor that could have gone bad once its warm. Just looking for ideas. Thanks for the help so far though, any and all help is appreciated. When does the stock fuel pump start to crap out though? I did check the spark plugs earlier after just replacing them a few days ago and the tips are white, indicating a lean condition so I thought perhaps the fuel pump may not be able to supply enough fuel when the bigger injectors are demanding it. And it being an intermittent problem suggests that maybe, its a voltage problem? Or perhaps something else?

Tune. And understand Open Loop vs Closed Loop engine operation.

You have too many other variables to "run 2g mafs with 510 and 560 injectors before without issue". Yes it's running lean, once in CL operation the O2 sensor is reading the lean condition and trying to add a bunch of fuel ( unsuccessfully ). Ergo crappy running.

Quit half-azzing things and get a chip or 'Link.

 

[EHmotorsports]

Get a Wideband and something to tune with, that has capabilitys to log.

 

Quoting ktmrider:
Tune. And understand Open Loop vs Closed Loop engine operation.

You have too many other variables to "run 2g mafs with 510 and 560 injectors before without issue". Yes it's running lean, once in CL operation the O2 sensor is reading the lean condition and trying to add a bunch of fuel ( unsuccessfully ). Ergo crappy running.

Quit half-azzing things and get a chip or 'Link.



While in closed loop operation would it not run rich...since all it is is the afr being adjusted by the o2 sensor. I would understand it running lean while in OPEN loop operation since the ECU's fuel maps come into play and then its up to the 2g maf to be able to try and balance the bigger injectors out. Either way I just bought a wideband so i'll see what those numbers are before going and buying something to tune with. Yes there are other variables but generally with that injector and maf combo it'll run rich at idle, but be pretty darn close at cruising and WOT.

 

[5OF2k]

Honestly, unless you plan on running speed density, get yourself a GM MAF/translator. You wont outgrow it power-wise, you can tune with it, and you can even compensate for injectors with it. Cant. Lose.

Get one and a wideband/logger, and you'll be good to go. Itd also be a good idea to get a bigger fuel pump, while youre at it.

-Jake

 

Went back to stock injectors and maf and same problem... /ubbthreads/images/graemlins/banghead.gif

 

[VR6Eater]

If this was a bone stock car and you were complaining of sputtering, missing and bucking at load and under boost, I would suggest plugs and wires. Having just bought a car and it drove perfect on test drive and next day went through the same thing. New wires and problem gone.

 

plugs and or wires were my first thought and the first thing i replaced with no luck. I'm picking up a maft, wideband and logger tomorrow so we'll see if I can iron out the issues. Thanks for all the help thus far!

 

So, still not sure what the problem ended up being but installed a MAF-T, wideband, afpr, walbro 255 and new plugs again and bam problem solved. I assume it was one of those things, or maybe a combination of them all. Thanks everyone for the help!

 

[460GVR4]

I like your thinking, replace parts until it goes away! haha that's what I did on my 90 talon.. She eventually broke my pocketbook.. Miss that car