fuel mileage drop off after blue spring?

[mtbxdrew]

Just installed the blue spring this weekend along with a new thermostat, was getting around 17-18, went and ran some errands after work getting 9mpg now! doesnt seem right to me. the spring mod doesnt add anymore fuel right? just increases pressures from what i can gather. Not seeing any smoke under load, at start up, driving etc... any one have any suggestions? Im half tempted to put the old spring back in and see if my mileage comes back.. fwiw i have the sct programmed on the canned street tune currently

[gman590]

are you operating temps normal?

[mtbxdrew]

180-185 on the scan gauge oil and coolant, changed the thermo out to get the temps up. temps actually dropped from 188 with old thermo to 180-185 with new thermo.. brand new out of the box motorcraft unit.. air temps are in the teens here now, worth covering the grill to get the temps in spec?

[Term3]

What's your fuel pressure, assuming you have a fuel pressure gauge.

[mtbxdrew]

Originally Posted by Term3

What's your fuel pressure, assuming you have a fuel pressure gauge.

no gauge, ill have to get in touch with my buddy to see if he has one

[Term3]

I'm assuming this is an actual Ford part as there are some springs sold out there which can push your fuel pressure close to 100 psi and that's bad for your injector "O" rings.

[mtbxdrew]

Originally Posted by Term3

I'm assuming this is an actual Ford part as there are some springs sold out there which can push your fuel pressure close to 100 psi and that's bad for your injector "O" rings.

yes it came right out of the ford bag, was the entire kit, o rings, spring, bolts, brass insert and cover

[legionxxii]

Are you hand calculating your mpg

[mtbxdrew]

yes, went from 15 stock to 17 with tune and exhaust, now down to 9mpg gonna swap the spring out and see what happens. no other reason for why it happened, except junk tank of fuel?

[ckyguy68]

Doesn't make sense. Even if you're fuel pressure is higher the injectors are only going to spray so much fuel. That is a MASSIVE decrease. I doubt it's the spring.