Well I just got a code 90 on my 99Si (b16) this is what the description for it says...
Evap Emission Control System Leak:
Fuel cap loose, poor vacuum connection, fuel tank, fuel tank pressure sensor, EVAP bypass solenoid valve, EVAP tow-way valve, EVAP control canister vent shut valve, EVAP canister, EVAP purge control solenoid valve

It's not the fuel cap, checked that. I did a half *** job checking the vac lines, Don't know where the FTPS is or the bypass valve (or what to look for when checking them). Don't know where the canistermabobber is nor the vent for it, and also have no clue about the purge control slolenoid thingy.

Any suggestions on this little mystery of mine????????
Thanks Damon

 

when you undo the fuel cap, does it relieve pressure ?
if so, you can concentrate on the evap canister box, located under the battery, it has two output, one thru the purge solenoid to the intake manifold and the other one goes the 2 and 3 way valve on the fuel tank....

if you don't hear a relieve pressure, ,then check the 2 and 3 way valves under the fuel tank...chekc your helms....

 

I don't have a helms, and there is pressure release, already checked that.

 

okay, look for open/tear vac hose on your evap lines....

if not, reset the ecu and drive it around until it comes back on again...it may be just a glitch

I had the problem before, but never get around to have it fix...

 

ok this might sound really dumb but can someone post or pm what exactly the evap system does? is it only for emisions or is it a mpg thing....

 

only emission, it has nothing to do with performance or gas mileage...

with hondata or any standalone, you can completely take out the evap system

 

does it hurts performace at all?