Fuelpump off o2 sensor?

[rustbucket]

Heres my problem:I adjust my fuel pressure to 49psi at idle (nismo regulator). Car runs perfect and strong. A few test passes later, when I hit WOT, and the car hits 5k rpms the motor hits a little blip and at 5.5 to 6k its completely running lean and sputtering like its hitting the rev limiter. I park and check the fuel press and it shows 40psi, I adjust it back to 49 and run it again, works fine for afew passes, then it happens again.

Wastegate is hooked to manifold and I'm running NGK bkr6eix-11s gapped at .8mm and a hybrid FMIC.

Question is does fuel pump work in conjunction with the O2 sensor? Or what else could it be?

Modified by rustbucket at 8:23 AM 8/29/2006
Modified by rustbucket at 8:24 AM 8/29/2006

[Joe]

you are leaning out and misfiring

this has nothing to do with the fuel pump or o2 sensor

are you tightening the locking nut at the base of the adjustment bolt on the nismo FPR?

[Darius]

What fuel pump are you running? Hopefully not the stocker.

[rustbucket]

Yea, I know its leaning out and misfiring. Thats why im asking what controls the fuel pump? The only conclusion I can come up with is that the pump isnt feeding enough fuel to the fuel rail.

Yes, the lock nut on the fpr was definately tight after each adjustment and I have a walbro 255lph pump.

[Darius]

I guess the part that seems fishy to me is that you have to keep increasing the pressure on your fuel pressure regulator. Why or how could it possibly loosen up to drop the idle fuel pressure to 40psi? Was it new when you got it or did you buy it used? I'm wondering if it doesn't have a pin hole leak in the diaphragm or something odd like that. For instance, it would hold enough pressures at low fuel pressure, but once the pressure increased, more fuel would slip past and drop the pressure to unacceptable levels causing lean conditions. God that's far-fetched!

[Carl H]

are you disconnecting the vac line when doing this to set your base pressure?base pressure should be 46psi with the vac line off and capped...

[gawdzilla]

thought its 43.5?

[rustbucket]

I bought it brand new. Believe it or not, the hole in the diapram idea flashed through my head, but im denying it because its brand new, the idea is far fetched, and I want to eliminate all the free fixes first.

The fact that I have to keep adjusting the fpr and turning the set screw in more and more makes me think the fuel pump is intermittant or not flowing right.

Carl H,It was adjusted to 49psi at idle with vac line attached and was running awesome, but it dosent keep the fuel pressure constant for long. If I get time today I'll try it at 46 with vac line pulled off.

[rustbucket]

Turned fuel down to 35psi and adjusted base timing, car runs perfect!