With a cold start, after the car warms to a certain extent, the idle will bounce between 1,500 and 1,700 and the fuel pressure gauge jumps between 30psi and 32psi or so.



Once I start driving it and it fully warms up, the idle is stable, but, when I hit the gas, full-throttle or not, the gauge bounces constantly between 30psi and 35psi.



In the Haynes manual it says the car should be running at a constant 35psi.



Now, I just replaced every damn injector seal, the fuel-pump is brand new, and everything is hooked up correctly. I even took out that nasty little Vortech Fuel-Pressure regulator.



My brother and I are thinking that it's the fuel filter restricting flow. Nothing else really explains it, but if you guys have any ideas, I could use the help.



The car itself is running like a dream though. We finally turned up my boost from 4psi to about 9 1/2-10psi, and it's fast as a ****. Last night my brother in his modded SR'd 240, T-28 @ 13psi, DP, BOV, etc... we were almost dead even. He barely pulls on me.



I am scared however that it's running a bit lean. I dunno! Help! >_<

 

Have you replaced the fuel filter



I have the stock S4 pump, a 240 sx pump (both intank), an Earls high flow filter, and all stainless steel bradied lines and am getting a constant 45 psi. I still dont have a regulator. I am just glad that my pressure doesnt drop after 5K. I forgot to hook my regulator back up when I put my manifolds back on and man what a difference.

 

do you have the pulsation damper in there?

 

No pulsation damper..



No, we haven't replaced the filter. That's the only damn thing we HAVEN'T replaced. LoL



Would that really explain it, you think? A clogged filter preventing flow, and causing fluxuation?



I don't even understand what the Vortech fuel-pressure regulator I had in, was supposed to do. When it was in, the car was damn near impossible to start up, I'd have to primer fuel into the motor even f*cking morning and even then, it was hard to start later on.



Now, it won't hold idle when I first start it. I guess I just have to burn up excess fuel. I do so by revving it a little or just holding it at like 2,500RPM for like 20 seconds or so, then it settles.

 

you need the damper, its job is to stabilise the fuel pressure

 

Shouldn't the car already have one? o_O



Yah, when I hit the gas it bounces constantly between 30-35psi, and sometimes I can feel it if I go full throttle. :/

 

the fuel pressure changes with boost / vacum. it should go up 1psi with every psi of boost.

 

it did have one

 

There's no way that it SHOULD be bouncing from 30-35 when I hit the gas though, and let me ask you guys.



When you start your car and it starts to warm up, does the idle ever bounce for you? It will for me until it's become completely warmed up..



Ugh! How frustrating!

 

the idle will bounce when the tps is bad, the ecu gets confused