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View Full Version : EVAP vapor purge line

NemeGuero
07-19-2005, 06:46 PM
So after removing the EVAP canister and all that stuff there's still the vapor purge line that goes to the rear of the car, to the fuel tank I presume. Anyway.. so there's nothing at the engine end to hook it to. My question is, can I hook that up to the extra vacuum nipple on the underside of the lower intake mani (after EGR removal) ? Would that be bad? Or should I just plug both ends?
projectRDM
07-19-2005, 06:50 PM
Leave it vented, do not cap it and do not pressurize it.
Pepperoni
07-19-2005, 06:57 PM
I left it uncapped a while back when i did a swap and i would just keep smelling gas in my engine bay. That's no good. I have had a hose running from there to the bottom nipple on the throttle body for about a year now and have had no problems. In stock form, doesn't it all end up at the bottom nipple on the throttle body anyway?
NemeGuero
07-19-2005, 07:39 PM
that's what I thought too. anyone else got some insight?
Flybert
07-19-2005, 08:02 PM
that's what I thought too. anyone else got some insight?

Yes, do what R240NA said and don't question us. THREAD OVER!!!
projectRDM
07-20-2005, 08:49 AM
I left it uncapped a while back when i did a swap and i would just keep smelling gas in my engine bay. That's no good. I have had a hose running from there to the bottom nipple on the throttle body for about a year now and have had no problems. In stock form, doesn't it all end up at the bottom nipple on the throttle body anyway?

Not directly. The vapors are purged and filtered through the EVAP canister first, eliminating most of the harmful and flammable parts before being reburned in the motor. By pumping it directly into the manifold without filtering it you're doing two things:

1) depositing excess film from the vapors into the plenum, creating more blowby in the crankcase.

2) adding another catalyst to the A/F mixture, causing pre-ignition and misreadings for the O2 sensor.

Though neither one is necessarily harmful, they will both cause poorer running conditions as the motor ages.

If you're concerned about vapor discharge under the hood, pull the hose from the rear portion of the line (coming from the tank) and run the hose into any open hole in the frame rail in the back. This is how the OE setup on OBD-I cars is done anyway, after filtering it's plumbed into a plastic fitting that snaps into the frame rail below the driver's seat.
Pepperoni
07-20-2005, 05:13 PM
That makes a lot of sense, and explains some things ive been wondering about. Thanks.