fuel pump question

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i have a 98 lsc and it seems like it loses power arfter 4000-4500 rpm at WOT does this sound like a fuel pump issue? last time i checked the pressure at idle in park the psi was 25 and once put in gear it came up to 35. and if it sounds like it what pump should i go with i was lookin into the svt focus pumps
 
Could be running lean, running rich, not enough voltage to power the coils, bad plugs, bad boots, bad gas......

Most likely NOT the fuel pump though. Tell us a bit more about the car. :)
 
when i started to drive the car it was fine but it did feel a little down on power then it developed a stutter around three grand which was fixed by plugs and boots i took off the muffler and have straight pipes but besides that no mods. and it has 51,000 on it with a motor that has 50600, on it (it was put in by the dealer) also has a new fuel filter less than a week old. also on occasion if i floor it off the line it stutters pretty good then goes after a second.
 
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Check voltage at the alternator and check for codes if you can. A shudder off the line is either a miss fire or possibly a torque converter shudder, a weak fuel pump won't cause a shudder, instead it would just feel sluggish.
 
if it were a the alternator that would cause the coils to not get enough juice during WOT and to not completely fire the cylinder right? also it does feel slugish in the high RPMs my 0-60 i timed at 10 second becuase it took so long to go from 4-6000 rpms
 
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alright ill do that thanks for the help and ill let you know how it comes what should the voltage be around for it to be good?
 
That pressure reading sounds low though. 25? But they are correct, it would not casue a shudder.

Voltage should be 14 volts, give or take. Below 12 is not good at all. Over 16 could be dangerous.
 
the shutter doesnt really occure anymore so i will check the voltage when i get out of work tonight and see how it is. its very probable thats whats causing the problem because it could have a bad remanufactured alternator on it.
 
While you're checking voltage, do it like this....

Car off, key off...test at battery, should be 12.4 volts

Car running at idle, NO headlights or a/c or stereo....test at battery, should be 13.8 +/- volts.

Car running at idle, headlights and a/c ON....test at battery, should be no lower than 12.8 volts AT WORST. If you idle up the engine while reading the volts, it should rise up to the 13.8 volts with a good alternator.

If you idle it up with the headlights and a/c ON and its still showing a low 13 or high 12 volts, that reman alternator is weak.
 
so i tested the alternator today this was my result...

car off batery test was at 12.7volts
car on idle showed 13.8 volts
car on a/c and lights on showed 13.99 volts

this pretty much shows the alternator is good so what else could be the sourse of my problem? this has really been bugging me:(
 
now that i have really indepth listen to the problem im 90% sure it is a misfire becuase it not always happening but now that the mufflers are off i can hear it much clearer.
 
Cool....all your power specs look great.

If it is a misfire, its most likely going to be a spark issue. Fuel problems are not that common when dealing with a miss. I'd suggest getting your car "scanned" for codes....I bet you have some. :) Even though the check engine light is off....it will still have stored codes. This will point us in the right direction.....if you go to AutoZone they will do it for free.
 
yes i will have to head up to the one near me this weekend do you think a superchips tuner would pick up a code i know they are much more simplistic but the due run DTC checks or do you think that wouldnt be able to pick up the code. i appretiate the help also.
 
Most tuners now-a-days will test for codes too. Also...once you get the codes read, make sure to post them here so we can help you figure it out.
 
so i plugged in the tuner at this is what it came up with....

P0171 - sys too lean (bank one)
P1519 - Intake Manifold Runner Ctrl stuck closed (bank two)

please tell me this is something easy to take care of...
 
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