5.4L fuel pressure 40psi too much?
06-08-2010, 02:08 PM
#3
The Mustang Guy
Thread Starter
Join Date: Feb 2010
Posts: 14
Likes: 0
Received 0 Likes
on
0 Posts
yeah well the truck is getting 13-14mpg...it has a CAI, 93 tune, flowmaster exhaust, new spark plugs...i should be getting 16 maybe 17mpg...2wd standard cab...and i don't drive like an idiot...i have a TT Mustang for that 
Last edited by 98Lariat5.4L; 06-08-2010 at 02:12 PM.
06-08-2010, 02:41 PM
#4
The Mustang Guy
Thread Starter
Join Date: Feb 2010
Posts: 14
Likes: 0
Received 0 Likes
on
0 Posts
update for future reference for everyone..i was correct in thinkin it was too high..justin at VMP said it should be at 30psi at idle with vacuum line on...i adjusted it down and we shall see if my mpg increases
06-09-2010, 02:08 PM
#5
Retired Aerospace
Join Date: Dec 2008
Location: Edgewater, Florida
Posts: 1,324
Likes: 0
Received 13 Likes
on
12 Posts
In the Loop:
That's quite curious since it's not the injector or fuel pressure that determines the air/fuel ratio by themselves. They are part of the closed-loop system with the HGOS. If the fuel pressure is high and more fuel than necessary is injected, the rich mixture will be detected by the HGOS and tell the PCM to adjust injector on-time to compensate. Similarly the CAI is just that....cold air and its effect on the intake air temp sensor. Chilly conditions tell the PCM to inject a little more fuel to match the conditions.I suspect the reduction of fuel mileage you have experienced may have more to do with the CAI and PCM strategy reprogramming than a seemingly high value of fuel pressure....anyway, keep us informed; knowledge is power.
