Excessive fuel tank pressure

[Frankie Figs]

I ran the FP on my 07 Si for about 1000 miles without any hiccups. I changed out the IM, TB, and injectors, switched maps, and now my tank builds a lot of pressure. I made sure the EVAP system is enabled in the tune and the EVAP hose to the throttle body has vacuum to it. Now, either my tank is building pressure or it's getting a lot of vacuum put on it to the point where it hisses when I remove the gas cap. This happens with a full tank or almost on empty. I almost forgot to add this, I'm having issues filling up too. I can't get a full tank because the pump keeps kicking off like its full even though it's not.

Can anyone help me with this, it's driving me nuts!

Thanks,
Frankie

[Hondata]

This could be caused by any number of changes to the fuel supply / EVAP system. You are going to need to swap whatever items in the fuel supply system / EVAP system which have been changed from stock, back to stock, until you isolate the problem.

I would suggest returning to the stock manifold, throttle body, gaskets & injectors first, running a stock equivalent calibration, then making one change every two tanks of fuel until you narrow down the cause.

[Frankie Figs]

That sucks :( maybe I'll start with the throttle body since that is directly connected to the EVAP system. If that doesn't help I'll move onto the harder-to-swap parts. Thanks for the insight! So it has nothing to do with anything in the tune?

[racefreek1892]

Mine has acted the same way with the whole pressure thing, it started right after i but on a base map for flash pro, i only have an intake header and exhaust, all three which i have had for over a year with no issues, this is some how caused by flashpro, how do we fix this?

[Frankie Figs]

I ended up disconnecting the vacuum line from the throttle body so the purge vent is open to atmosphere. Just don't tell the EPA! They might get mad lol