Replaced 02 sensors (pre cat) and the little Bosch vacuum solenoid valve thing I’m suddenly drawing a blank on the name for that sits beside the throttle body. Wow. Brain. Work.

 

Purge Control Valve. Check the gas cap is seating fully.

 

I thought these Discos didn’t have PCVs per se. (both of mine have The Mod)

I checked the gas cap; so maybe it just needs to be replaced.

 

Believe "Best" is talking about purge solenoid. Which is mounted behind throttle, above tappet cover, DS. But, check your fuel cap first, like recommended.



PCV stands for Positive Crankcase Ventilation.

 

Purge Control Valve from Hyundai OEM Genuine

 

Most likely the purge valve. I got a genuine Bosch on ebay and it worked right out of the box. I tried a Hyundai before and didn't work for me.

 

Got it got it, yeah that’s the thing I mentioned I replaced in the original post that I couldn’t recall the name of. I guess that just leaves the gas cap?

 

It leaves many things besides gas cap: faulty purge valve, hoses, vapor canister, vapor detection pump, vapor separator. Workshop manual p. 17-4-2 shows all that is involved. The ECM throws P0440 when the oxygen sensors can't detect vapor flow from the purge valve. First, I would check the purge valve again and that the vapor lines are not blocked or leaking. The inner layer of the hose can separate and block the flow. I had that problem at the hose end sitting on the purge valve input. I just cut off one inch and then it looked good. It was not the cause though.

 

You MUST get the OEM Hyundai unit in OEM packaging. Dorman, BWD, and other non OEM Purge Control Valves are pure crap. Either Bosch or OEM Hyundai = only way to go period. I have installed probably 100+ OEM Hyundai units without a single failure/issue.

 

I got an OEM Hyundai in the OEM packaging, yep!