ParkerSS

iTrader: (2)

Wondering if my fuel pump is failing or just doesn't flow enough for my application and is causing this problem.

Car has 435RWHP in an A4. Mods in sig.

When I could start or warm start I have to prime the pump about 3 times and it'll fire up and idle low then slowly build up to where it should be. Also if I rev it it will build up fast and at WOT it will blow a good bit of black smoke and smells like fuel pretty bad. But if I shift into reverse or drive before I let the idle build up warm or cold it will drop real low and stutter pretty bad and sometimes die and if I foot brake it and drive it away before the idle has built up it will spit and sputter. After the idle gets right though it's fine and will stay idling when coming to a stop with no problems but if I shut it off I have to start all over again.

Car has new plugs, wires, IAC, TPS, checked all fuses, new fuel filter, and new FAST 36lb injectors, and new MAP sensor.

Car ran fine for weeks and suddenly began doing this after going WOT a few times one night.

If I need to upgrade though I'm looking at a racetronix setup but will that include a new fuel pressure regulator?

Just wanna make sure this is probably the cause before I spend $200 on a new fuel system.

Stock pump has never been replaced and neither has the FPR and they have 85k miles on them.

Thanks guys!

5.0 LsX

iTrader: (7)

have you had it tuned? sounds like its running to rich

BlackChicken

The stock pump can't keep up is what it sounds like, upgrade to a walbro 255 and that should take care of the problem. Or you can try to run some bg44k fuel cleaner and see if that helps.

SOMbitch

iTrader: (8)

The stock fuel pump can EASILY support 435 rwhp. My 346 made 434 and never had a fueling issue and I have seen one pushing 470+

It sounds like a tune issue but you said it didn't always do it. I would prolly change the filter and test your fuel pressure.

And no neither a Wahlbro or Racetronix comes with a FPR.

RPM WS6

iTrader: (3)

Black smoke is a clear and classic sign of running too rich, not too lean, so it sounds like the pump is doing it's job under WOT.

I'm not sure that your problem is fuel pump related, based on what you've posted.

Does it crank for an exceptionally long time on a cold start, longer than ever before?

Seems like the fuel system was enough to keep up with your power level, but that something may have happened during those WOT runs. Have you noticed any other issues, like new engine/valvetrain noises? Have you done any PCM scanning yet? If you have an OBD scanner that can read O2 sensors, you could run a graph/log for a WOT run and see if the readings lean out under load. I doubt they will though, since you mention the black smoke.

I'd also scan for misfires as well as LTFT & STFT data.

ParkerSS

iTrader: (2)

Yes it's been tuned and logged and me and my tuner can't figure it out. It's really weird. Everything sensor wise is working fine and on cold start if I prime the pump it will start up fine not any longer than before from what I can tell. And I already put in a new filter. I'm gonna try and see if taking some fuel out in the tune will help but it just feels like when you start it it's choking and then a few minutes or seconds later depending hot or cold it will bring the idle up to where it's supposed to be.