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Correct fuel pressure in '03 with 3.0 flex


williamigriffith

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I believe I have a very lean condition that I have described in an earlier post. I routinely get the following codes: misfire on 4,5 and 6 with a lean bank 1. If I drive gently around town, no problem. If I make the truck work harder, particularly a long grade at 60 mph, it cannot maintain speed and the CEL immdediately starts blinking. If you depress throttle until downshift, it knocks like crazy at the higher RPM and you have to let up on the throttle. Bottom line, I have replaced air filter, fuel filter, plugs, wires, cleaned MAF and TB. I don't think it has anything to do with the catalysts, as the engine seems to rev ok to 3k under light load (accelerating in lower gears at low speed) All that seemed to be left to look at was O2 sensors and Fuel Pressure. Today I measured the fuel pressure, and I am a bit confused.

When I just turn on the ignition and don't start the truck, the pressure is between 14 and about 20psi, it is never exacatly the same. When I start the engine it goes up to 60 psi at idle, and stays there. From what I got from other sources, I thought the fuel pressure was supposed to drop a bit from ignition on not running to engine idling. Does the above sound normal? If the pump is supposed to be running until optimum pressure when the key is on, this one doesn't do it. On the other hand, pressure seems quite normal when running.

Any comments on the correct fuel pressure or the lack of power would be much appreciated. Thanks to several of you that have already suggested "seafoaming" and checking out O2 sensors.

Griff
 


Rock Auto 5% Discount Code: 7FA902352B4C01: April 5th, 2021

Rearanger

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All I can do is give you are the specs from my FSM;
Key on - engine off, or engine running: 64psi +-8psi.
 

TomB1269

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Have you tried Seafoam to knock out carbon buildup, and MAF cleaner to make sure you are getting the right info to the ECM.
 

williamigriffith

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Responses to questions

Rearanger, thanks for your reply. Is that spec for the 3.0 flex model? I've have heard that it is different from the gas model. Thanks for checking.

Tom, I did the seaforam and MAF cleaning, but found no improvement. I am considering changing the O2 sensors, but I need better supporting evidence.

Griff
 
Last edited:

bikerboy

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Here's the spec

Item Specification
Key on, engine off 414-448 kPa (60-65 psi)
Engine running 414-448 kPa (60-65 psi)
 

Firecracker

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I’m having the exact problem and I just found this thread, still new to this forum(any forums actually, this is my first account LOL) 3.0 2003 with same codes, same issues and I’ve changed plugs, gapped correctly, bank 1 O2 sensor, new wires, cleaned the throttle body, new IAC sensor and no differences... fuel regulator at 65psi at idle and all the way up to 3k rpm. 12 years later, has
anyone figured out the issue?
Thanks! -Firecracker
 


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