Fuel Pressure/Idle problem 5.0

[Dash71121]

hey guys, so im having a little problem. When i start the truck up it idles nice and smooth at 900-1000 rpms and at 34ish psi fuel pressure. After idling for a bit it drops to about 800 rpms, runs rough and very rich and fuel pressure jumps to about 40 psi. this also happens when im driving around and am sitting at a stop light for too long. I bought the bronco2 with the 5.0 already swapped it in and it has been doing it since i got it, but now its getting worse and has died on me a couple times when it makes that switch in pressures.


also when i rev the engine fuel pressure drops to 30ish psi.


thanks, dylan

 

[RangerSVT]

Check the FPR on the fuel rail, as well as the vacuum line feeding the FPR...Do you have any more specs on the setup, what year motor it is, whats it out of, etc??
SVT

 

[Dash71121]

its out a of late 80's car, it has the mustang intake though. i noticed a while after i got it that there wasnt a vacuum line going to the fpr so i hooked one up and it seemed to make it worse.. so maybe i do need a new fuel pressure regulator?

 

[RangerSVT]

Mustang style intakes came on a number of different vehicles...If the throttle body is facing the drivers side, then its out of a lincoln, if its a passenger, then its out of a mustang or cougar/thunderbird...And yes, I would look into changing the FPR....
SVT

 

[Dash71121]

thanks, its on the passenger side.. i think it did come out of a thunderbird