signs of a bad FPR? aweful idle and off idle

[Grifter]

what are the signs of a bad FPR?
i'm trying to track down an idle and low RPM issue..
car info: cobra intake, fuel rails, 30#'s 255hp pump, rail mounted fuel pressure gauge, 38-39# pressure at idle w/ the vaccuum line off the FPR

if i turn the key, let the fuel pump cycle before i start it, it idles rough and off idle its rough. sounds like it has giant cams, and misses and sputters. at cruise its fine. pull up to a stoplight, and it misses/sputters a bit.. like smaller cams, and is a bit chunky off idle, but not as bad as during startup.

if i just hit the key to start it, not waiting for the pump to cycle, its not as bad, but still a little rough. off idle is aout the same.

i cant seem to find any vaccuum leaks (not ruling them out though)

thinking that maybe i am overrunning the stock FPR?

 

[1wykdmk8]

I am not totally sure, but I know that the factory FPR can not regulate the pressure from a high pressure fuel pump for too long. I would say since you spent all that money already then why not spend the $90ish for a Kirban FPR from JD's Performance.

 

[driller]

I had similar issues way back. But I had replaced the regulator first then had to replace the fuel pump as it failed the leakdown test.

Actually, your description sounds to me like an injector problem?

 

[Grifter]

i had wondered about that too, but theres shouldnt be an issue with them, they are new injectors.
would the ECU handle me swapping back to 24's to test that theory out?

 

[Dr. Paul]

i had wondered about that too, but theres shouldnt be an issue with them, they are new injectors.
would the ECU handle me swapping back to 24's to test that theory out?

Why do you have 30# injectors on there? Is the MAF calibrated to accept that? Do you have a blower?

 

[driller]

Do you have a tune for the 30# injectors? I'm not sure if the stock ECU can compensate enough for the bigger injectors. It can only do a certain percentage then throw a code.

 

[brentalan]

I've been using a stock FPR with a 255lph pump for over a year now, no issues - knock on wood.

 

[Grifter]

you dont "calibrate" a maf.. the tune adjusts around your maf's transfer function. you can throw a C&L in there with the sample tube BS and trick the computer, but you will never find a C&L in any of my cars..

well i am "supposed" to have a chip setup for my current combo, but i think they just threw my old tune on a chip and sent it to me by mistake. i threw my 24#s in there, pulled the battery terminal, let it sit, fired it up and it idles awesome now.. so i think i never really had a tune for my 30#s like i should have..