Low Fuel Pressure

J

jtmforever

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I have a 1995 Mark viii that has idle pressure at 31 psi. When I press on the throttle and hold it at say 5000 rpm, the pressure will spike to 41 psi and then go back down to 31 psi. WHen I unplugged the fuel regualtor, it always stayed at 41 psi idle and wot. Is my regulator going bad?
 
But i thought that when you hold throttle at high rpms, the fuel pressure suppose to stay at 41 psi until you let go of the throttle
 
In park, isn't that the rev limiter, at 5000 thousand? Sure the computer tells the engine to quit firing, and reduces fuel pressure? Just what I think.
 
1.) do you have a drivability issue?
2.) Like Chris said, vacuum controls fuel pressure. When you accelerate from idle to 5k, that is a load, thus causing a need for more fuel volume.
2.) If you watched fuel pressure while driving, you would see you fuel pressure almos move with the accelerator pedal.
 
ok the problem with my car is that it idles rough all the time. I've researched that it could be the iac, tps, camshaft sensor, or o2 sensors. I am changing the iac, tps, and camshaft sensor this weekend. Also when my car is in 4th gear, it shutters badly. I guess i need to flush with mercon v.
 
Sounds like a misfire... I would look into that before you replace all those parts.
 
That's the main that kills me about this site, why can't we have it all catagorized ..something like LOD, but even that system can be improved

New guys always find it difficult to use the search, of maybe everyone's just lazy...I.don't know anymore, ill go back to sleep- dayum insomnia
 
I prefer it the way this site is set up, everything in one category. It is the main reason that I prefer this site over LOD. I understand that it may be annoying when people repeatedly make threads on the same topic, but the way our site is setup makes it feel more social...if a thread annoys me, I just stay out of it, I like that we can sort of shoot the **** around here because of the single subject forum.

Anyway, if you have a rough idle and a constant roughness in OD, I still bet it is a misfire... Replacing your plugs and wires doesn't automatically mean you can't have an ignition/injector issue.

Is your shutter in OD an intermittent thing? Or all the time?

An IAC will not cause a rough idle, it will either cause it to stall, or idle too high.
The TPS also will not cause a rough idle condition.

Just food for thought.
 
Try swapping coils from the running mark...see if that fixes the misfire. Also what wires did you buy?, the cheap AZ brand wires don't really fit well. I know because I bought em and returned em so I could buy motorcrafts. They just don't seem to snap into place, and my mark had a misfire becAuse of that. Motorcrafts fixed the problem.

Oh, and the plugs need to be gapped correctly or you'll still have a misfire . I know the plugs say they come gapped, but you still need to check them.
 
Put a damn gauge on the fuel rail with a hose, run under the hood so you can see it while driving and watch for fluctuations under load.....
 
I bought the wires from autozone. The car runs perfect except only at idle or when i let go go the throttle. The transmission always shutters in 4th going 40 mph. How can I only have a misfire at idle and not above it? I hooked up the obd1 scanner and found out hego Bank #1 is lean and not switching on. I also have a 524 code. I am changing the o2 sensors next week. Can this cause my sonstant rough idle?
 
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