2003 Targa, TIP having some idling issues...

The other day after fully warmed up (80 degree day) RPMs shot up to 2k when putting in park. Blip the throttle and they'd stay at 2k and very, very slowly settle.
On a cold start the next day after the air pump runs, it'll hunt, bouncing around 500-800 RPMs.
Got a CEL and a scan with my VCDS shows "P0456 - EVAP System: Very Small Leak Detected".

From my searching it could be a few things like Fuel Line Vent Valve (no howling from the filler area and no trouble filling up), Electric switchover valve coming off of throttle body, Vacuum Reservoir, Hoses.
Just looking for direction on where to start with these, or anywhere else to check...I don't wanna $200 myself to death swapping parts.

Diagnosis I've done so far:
New gas cap last year, which took care of a P0442 I was having previously...no effect on idle.
Oil cap off...no effect
AC on/off...no effect

Thanks!

 

Do a smoke test and find that vacuum leak.

 

Agree, but do an e-gas calibration first. Put key in ignition and move to RUN position (not start). Wait 60 seconds and then turn off ignition. DO NOT TOUCH THE ACCELERATOR PEDAL DURING THIS CYCLE. You should hear some whirring and clicking noises from the engine bay.

 

Ordered a smoke tester, should be here tomorrow...hopefully it'll find a hose leak and I don't have to go chasing broken valves.
E-gas cal didn't do much, still hunts the idle - makes sense if it's got a vac leak somewhere.

 

While you’re waiting on your smoke tester…..
you could clamp off hose between evac purge valve and throttle body and see if idle improves.

 

Did you get new tires recently?

 

Are you talking about this hose?
Tried clamping it off with some hose-pinch pliers and no change...still hunts


Quick edit: If I grab that hose in question, I can feel the vibration of that valve tapping away

 

Yeah that’s the hose. You could take hose off valve, plug it with a center punch or something similar and see if valve still taps. Might be valve isn’t staying closed.

 

I ponied up for a new set a couple of seasons ago.

Have you replaced those rear tires yet?

 

Update:
Did the smoke test today and was 98% sure the smoke was coming out of this little port-hole on the rear plenum:

I called my wife out and asked "where's the smoke coming from" She points to that and said "from that little black nipple"
Soooooo, how common is it for that to leak and I'm guessing a new plenum is in order huh?
I didn't see anything else in that area as far as hoses that would/could leak either.
It did build up quite a bit of pressure before smoking and blowing the smoke machine adapter out of the intake into my face...so small leak as the code did say.

Edit: it's the pivot-point for the resonance flap...found a thread where a guy found little caps that fit, so I'm gonna try that for the time being

 

Find a plastic cap thats larger then the pivot and epoxy it over the stem. There r no parts to fix that seal and its a fix thats has worked well in the past.

 

Right on, that's the plan! Off to the hardware store tomorrow

 

I would figure one of those 2 part putty stucks would be best. Put a bead around the lip and squish in so it seals the irregular surfacr

 

If sealing off/stopping the leak on the resonance shaft doesn't fix the hunting idle, then get a manometer and test the AOS function..Should be 4-6 inwc ..

It will not show on a smoke test ( maybe a little smoke from the tiny atmospheric port way back on the engine) but if failing will cause the idle to hunt as it can't control the flow of blow-by to the engine...

 

Ugh not the AOS! Aight I'll check that if the cap doesn't work.
Thanks!