Is your fuel pressure still jumping around?

 

It could be unburnt fuel igniting.


Just some food for thought.

 

Yea still jumping from 40-60 psi, scanned it and the only thing it said was lean fuel mixture on the o2's

 

Could be a lazy O2.

 

Possible, anyway to test o2's?

 

Thought it could be a vacuum leak to the regulator but it's pulling 20lbs at idle, clueless now

 

I've never seen an LS1 running factory fuel calibration software use a vacuum reference on the pressure regulator.

The damper on the fuel rail has a reference, but that device isn't a pressure regulator and the PCM assumes a constant 58psi (assuming constant voltage).

If you have a pressure regulator running w/ vacuum control, I'd try removing and capping the vacuum source.

 

It's a ls swap into a 96 bird which uses a regulated return style fuel system so I'm running a professional products fuel rails and billet regulator

 

What is your rail pressure with the reference hose removed from the FPR (at idle or at any rpm)...?

Have you noticed any gasoline inside the reference hose...?

When did this start to happen...?

 

Rail pressure is 55-60 with it removed 40-60 with it on, never say any gas where it wasn't supposed to be, and it started last Friday but has done it before but always cleared up in a short time

 

Any chance you'll try disconnecting and capping the vacuum signal to your fuel pressure regulator?

 

Hell I'll try anything once, how would that fix it? As much as I want it fixed I also wana know how and why

 

I "wana know how and why" you decided to feed vacuum to your fuel pressure regulator.

As I said previously:

This means the PCM does not expect the fuel pressure to vary. The way you have your fuel press regulator connected to vacuum, the fuel pressure is varying.

The symptoms and error code you're seeing are indicating lean air:fuel ratio.

Your regulator is reducing fuel pressure at high vacuum periods, which would reduce the volume of fuel delivered...causing a lean air:fuel ratio.

So remove and cap the vacuum signal to your fuel press regulator and re-test.

 

I'll try and see, according to the instructions that came with my rails and regulator the reg needed to be plugged into a vacuum source on the intake so that's why I did it.

 

That's understandable but wrong for the LS1. The PCM is configured to assume 58psi constant delivery pressure.

Other systems like the older TPI had vacuum-modulated fuel pressure and they were calibrated in software accordingly. Not the case w/ LS1s.

I think you'll be happy w/ the vacuum removed and capped from your regulator.

 

I tried it, it helped but it still is doing it(SOB) I have a video and some pics of my setup to help get a idea. The pressure guage is on the rail if that helps, about how far should the fuel line push gas out on it's own? I'm thinking it may have blockage or a bad seal in my regulator. But Im loving the help you guys are offering Thanks a load

 

here are the pics, Ill have to upload the video later, however Im going to try and put a new relay in again, its a new one but I dont trust it.

 

You definitely need to find and fix the cause of your remaining fuel pressure variation. The red MSD ignition coils have many reports of failure and you'll want to keep an eye on them, but they don't cause fuel pressure problems so put them on the back burner.

If your fuel pressure continues to fluctuate w/ the vaccum signal disconnected and capped, I'd say it's time to get scan data. It's possible your voltage is fluctuating and causing the fuel pump to intermittently underflow but no way to check that over the Internet.

 

How would you check that?

 

With a scan tool.