1BadZ95

Ok I have a high RPM miss. I have 30lb SVO Injectors and a fuel pressure regulator. We have had the fuel pressure set at stock PSI but the other day we raised it a couple psi and it seemed to help the miss a little bit. So my question is. With this fuel pressure regulator it keeps the fuel pressure at the same PSI from Idle to WOT. So I'm wondering if I should raise the fuel pressure to what it should be at during WOT? It's kind of hard to explain but maybe some of you can get it lol.

93transam1234

As long as it is set at around 45 PSI then the computer will ajust it for idel and lower rpms, I am sure you have heard it a thousand times but i also had a high rpm stumble 5500 and above. It turned out to be my opti (it was corroded inside)

I have also heard people fixing that problem with new wires, smaller gaped plugs, new coil, ignition control moduel

It took me over a year to fix mine because i didnt want to beleave it was the opti

Injuneer

Are you saying you are running a fuel pressure regulator that is not vacuum compensated?

If so, you need to set it at the pressure you told your tuner you were going to be running with the injectors you told him you would be running. He set the injector flow constant in the PCM based on the injector size, the pressure the injectors were flow rated at, and the fuel pressure you told him you would be running. If you didn't tell him a fuel pressure, he logically would have assumed that you were running 43.5psi = the stock LT1 pressure.

Hopefully you also told him you were not running a vacuum compensation line, because that will affect the tune.

1BadZ95

It was tuned by Ion, he has it set at stock pressure.

klrz28

mine is set at 50psi at idle holly tb no problem on my 383

1racerdude

In other words, he has the computer set for 30# injectors and 37 at idle and 47 at WOT. Is this correct? And you have changed nothing since the tune,correct?
What FPR do ya have?
What is the idle/WOT pressure now?

1BadZ95

I guess thats what he has it set at, he doesn't give all those details. Last night we hooked the fuel pressure gauge again and taped it to the windshield so it could be seen from the inside. We went for a cruise and at WOT under a load the fuel pressure drops way down, from about 44psi to around 35 psi and this is when the missing starts. First thought of mine was, maybe the fuel filter is clogged and not letting the fuel through. So this morning I bought a new filter and it didn't help. The missing doesn't really feel like its starving for gas though, it feels more like an electrical problem. Were going to switch out LTCC boxes and see what that does. We tested the coils and the resistance seems ok in all of them. We looked at all the wires and nothing seems hurt, all the grounds are good, theres no flashing lights in the LTCC box. The plugs are new TR6's and the plug wires were recently changed before this last rebuild. I'd say they have about 1500 miles on them max. This opti has maybe 2500-3000 miles. Its not throwing any codes, theres no code history. The miss is only under a load at WOT. I can be WOT spinning the tires in first, second, third, and theres no miss until it hooks up. Any ideas?

1racerdude

If your FP is falling that low it IS the pump.
Change it.

1BadZ95

Well after we do the LTCC box and if that fixes nothing (have a strong feeling it won't) but try anyways. That was our next guess after the fuel filter. But man the fuel pump is a PAIN IN THE *** on these cars! Whats this "trap door method" I hear about sometimes? Does it make it alot easier? Also whats a good pump for me, shouldn't ever go over 500hp?

1racerdude

Racetronics. Well, do ya want to fix the miss or not?
Do a board search there are diagrams floating around to cut the hole. Just make it bigger to the left by 2".

madwolf

I always program for the stock 43.5 PSI unless asked otherwise. If your fuel pressure is dropping at WOT, it is your fuel pump. Replace it before you put a few holes in your pistons.

1BadZ95

That's the plus to Forged internals! lol I'll get on that was savin up for a paint job but havn't done it yet because of this problem, I figured I was going to have to spend some money. Well next thing on the list, fuel pump asap! Thanks for all the input and help guys. Any other suggestions let me know.

Injuneer

You never answered my question about whether you had a non-vacuum compensated fuel pressure regulator. That would be the only explanation for a fuel pressure regulator that "keeps the fuel pressure at the same PSI from Idle to WOT". That would affect your part throttle tuning.

Its no problem running without vacuum compensation... I use a Weldon AFPR without vacuum compensation, but the tune reflects the fact that the pressure never changes.