Quote:
Originally Posted by layinrocker65
I have no experience with stock flex fuel LSs but I can tell you that the early style LS truck rails with the regulator in them sets the fuel pressure to 58psi.
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Swapped in a 12 bolt with lower gears on my days off, so I didn't get back to this idling issue. Found some comments straight from the Ford repair manual at the links below that reinforces your statement, "Non flex fuel engines, fuel pressure spec is 55 to 62 psi with vacuum line disconnected, fuel pump running." That would put it about 58PSI mid range with vacuum line disconnected on return style, non-flex systems.
https://ls1tech.com/forums/fueling-i...injectors.html
http://www.lt1swap.com/identify_vortec_engine.htm
Also found that the flex injectors are rated at 8PSI less than non-flex injectors, "25326903 - 5.3L L59 Vin Z, flex fuel 5.3L - flows 4.164 gm/sec or 33lb/hr @ 50 psi".
Thing is that the low end of acceptable range for non-flex systems is 55PSI and my flex is running 54PSI with vacuum disconnected. Assuming my gauge is 100% spot on, I doubt 1PSI is going to make a lot of difference with the idle. I'm still thinking tune or something outside of the fuel system altogether.
I will look further into the throttle body for vacuum leaks this weekend. Thanks for your continued help!