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The beast from Brazil
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Will it also die when driving, or only when idling? Could you give the exact codes you where getting? Did you change the fuel pump for this problem, or was something else going on? Low fuel pressure can be caused by a faulty/clogged fuel filter/pressure regulator, but fuel pressure related problems will normally give problems during acceleration and higher rpm´s.
A faulty O2 sensor could make the fuel/air ratio too low and the engine will simply die. That could explain that it will run ok for the first 15 minutes (still in open loop mode and not using the O2 sensor(s) for fuel fine tuning) and gets the problem when it has warmed up (now in closed loop mode and using the O2 sensor input for fuel fine tuning).
 

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The beast from Brazil
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8,310 Posts
So did you change the fuel filter/pressure regulator already? Also a vacuum leak has influence on the idle speed. With the engine cold, the evaporative purge solenoid doesn´t work, but it will after warming up. So when there is a leak in the evaporative system, it could influence the idle when warmed up.
 

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The beast from Brazil
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8,310 Posts
If there was a lot of debris in the tank, i would change the fuel filter/regulator.
Did you check the evap lines? They tend to give problems on the rubber parts close to the rear axle. They dry out and break.
 

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The beast from Brazil
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8,310 Posts
The one at the pump is just an inlet screen, not really a filter. You will find the filter/regulator just in front of the rear axle on the left side. There is a writeup in the DIY section of the WJ regarding the filter/regulator change.
 

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The beast from Brazil
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8,310 Posts
Did you check the vacuum lines going to the evap canister behind the left rear wheel? These lines pass around the rear axle, where the rubber hose dries out and breaks.
 

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The beast from Brazil
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8,310 Posts
If you want to know if a leak in the evap line is causing the problem, you could easily plug the line under the hood. The purge solenoid is mounted on the left fender (seen from drivers position) and you could follow the lines to see which one is going to the engine inlet duct. You could plug that one temporarely to test. But you have some vacuum leak for sure if you hear a hissing noise at the rear, so you better just try to solve that and be done.
Never touched the fuel lines, but as far as i know will the fuel pump run constantly when the engine runs and will the fuel pressure regulator in the filter assy regulate the fuel pressure to around 45 PSI (when im not wrong about the figure) and will the surplus fuel be send via the return line back to the tank.
 
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