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 mofo. 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 https://www.nopistons.com/forums/pub...IR#>/wacko.png

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

Well change that fuel filter and get back to us. Check your plugs to see if you are running lean. White = lean.

always start cheap, 75% of all fuel problems are the filter.

A fuel filter for my old hachi was like $45, how much will one be for my FC? I only ask because I'm so short on funds atm, lol

What if I took out the fuel filter and just hooked up the line to itself for like, 1 day.



Would that be not worth the risk?

your fuel pressure is fluctuating because it is directly affected by vacuum. since your idle is hunting your pressure will move accordingly. find out what's going on with your idle before you blame the fuel.

It will idle fine before it's warmed up, but when the idle is unstable @ 1,500-1,700...the fuel pressure bounces with it from 30-31psi.



For some reason, after driving it, and parking it, at the end of the night after maybe going full throttle to 5k or so a few times, the idle will sit really high, but not bounce, and when it did it last time, the temp gauge wasn't even past 1/3..it was odd cause the idle was stable @ 1,000 all the way home..

if you fix the idle problem the fuel pressure problem will be fixed too.

can i see some data or pie graphs? https://www.nopistons.com/forums/pub...IR#>/blink.png

mmmm pie graphs

I found out that the fuel filter is new, just like my fuel pump. We're talking 2 months old.



It's so messed up. When I hit the gas just barely over what you would to maintain a constant speed on a flat road, it bounces between 31 and 36psi...



I can't figure it out!!! Also, when you let off the gas, the car jerks kind of violently back, and as soon as you touch the gas, it'll jerk back foward and then accelerate. *sigh*

So if you hold the gas at a constant rpm it still bounces?

If you just BARELY hold your foot on the gas to cruise at a definite speed like 45MPH, it'll stay at 36psi. If you hit the gas ANY harder than that, it'll bounce between 31-36psi.

so you took out your fuel pressure regulator and you are wondering why it changes now?

It did it when the FPR was installed.



That thing was evil, it caused even MORE problems.

lol no graphs, just speaking from parts sales experience. Most fuel related issues we can solve with a filter. Wasnt speaking RX7 specific.

We put the fuel-pressure regulator back in...(the right way)



Didn't make a difference. :[



wtf