what would cause my fuel pressure guage to bounce?

[BHack3tt]

s13 sr swap, with basic mods...

lightweight pulleys, downpipe, exhaust, fmic, bov, z32 mafs.

when I am just coasting the gauge bounces from lean to rich without even touching the throttle...

[LayNLow]

So which is it, fuel pressure gauge or a fuel to air ratio gauge? What kind of gauge?

[BHack3tt]

Tells if the fuel is rich or lean

[filipino4life92]

prob means A/R gauge, tells if your starving your engine or giving it too much "food."

how many lbs of boost you running? cuz the amount of boost you run determines how much fuel pressure you have to increase.

ratio i think is 1:1. so if you're running 12psi of boost then you increase fuel pressure by 12lbs.

my buddy is running round 10psi, and he had his stock fuel pressure at around 34psi and his air/fuel ratio would jump from 14.5-15 then back down and up....basically what yours is doing. gonna sound weird but he increased his fuel pressure by 10lbs and now he's running a steady 14.3....

basically all you need to do is play with your fuel pressure (given that you have a fuel pressure regulator) and just follow that formula (boost:fuel pressure ; 1:1)

[fliprayzin240sx]

Tells if the fuel is rich or lean

So you have im assuming you have a christmas tree light thats hooked up to the stock Narrow band o2 sensor. Throw the junk away cuz its shit.

Get a real wideband o2 sensor gauge and then figure out if you're really running lean or not. Stupid narrow band sensor just freaks the fuck out since it cant keep up with the readings.