Golf Mk4-Issue: 16825-EVAP Emission Control Sys Incorrect Flow

**RustySocket** · 25-03-2024,03:17 PM

Car details: Golf MK 4, 2001, 1.6 16v AZD, petrol, hatchback, 223,000 miles.
Fuel system & engine management: Electronic multipoint injection; Bosch MD 7; Magneti Marelli 4LV (I think).

Owned the car 10 years, approx. 124,000 miles.
Original engine (as far as I am aware).
No known changes to mapping.
No known changes to cat or other emission systems (excluding repair\replacement).
Servicing carried out as per handbook/Haynes intervals.
Car only used for sedate SD&P, commuting.
Battery less than 6 months old; Engine cranks fine, no light dimming.

About 160 miles ago:

MIL light, code 17818. "P1410 - Tank Ventilation Valve Circ. Short to B+" / "EVAP Purge Valve (N80): Short to Plus"
Engine suddenly began “hunting”, misfiring.
Visual inspection, no obvious split pipes, broken wires.
Code cleared.
Fitted new “N80” solenoid valve.
The original looked like it was the factory VW part.
The replacement was supplied via a seemingly reputable, established online company. Part:NTY EFP-AU-002
On starting, it *seemed* better, but the misfire was still present.
MIL light, code not recorded, but indicated misfire on cylinder one.
Replaced cylinder one ignition finger/coil.
Cleared code.
Ran up to NOT, test drive: No misfire. Sounds fine. No MIL.

Current situation:

Whilst steady motorway driving:
MIL light, code 16825 - "EVAP Emission Control Sys Incorrect Flow"
No misfire, no other symptoms.
Removed N80, no obvious petrol smell from evap canister.
Blowing into disconnected, removed N80: No air flow was noted.
Airbox/throttle body gasket in good condition.
Cursory examination revealed no obvious splits, fretting or broken wires but currently enjoying persistent “showers” of spring sunshine, so haven’t got any further in the investigation.

The image shows the what I think is the evap canister and what I think it the N80 valve (removed). The shiny stuff on it is a bit of silicon grease.

Has anyone got any ideas where to start with this issue (16825), or any specific knowledge of it (ohm values, voltages, etc)?
That is, what obvious and not so obvious checks I could I carry out and is there a typical “culprit” for this error?

Also: I didn’t really understand the meaning of the original code (17818).
Specifically, “short to plus” or “short to B+” - in terms of short circuits/ broken wires, etc., what does it mean?

Thank you.

IMG_20240325_093531745.jpg

**RustySocket** · 18-04-2024,08:30 AM

Update:
Eventually there was a gap in the rain and I took another look.
I found that the hard plastic vacuum pipes from the "back" of the throttle body, to the brake servo\booster, were splitting where they mated with the plastic connectors.
Obviously none of the splits were on the "front", visible side…

The pipes come in two parts, so both were duly ordered.

I ordered them from ******* and another supplier from “beyond the wall”, as for some reason, a few years ago, prices in the UK went nuts and the number of suppliers drastically reduced. Benefiting because “they need us more than we need them” and the impressive increase in red tape we now enjoy, the delivery took ages.

1J2-612-041 D - The longer of the two.
It came with some heat protection the original did not have but was otherwise identical.
Viaco part was: V10-3626

1J0-612-041 BK - Shorter, with one way valve.
(The original valve worked OK, when tested).
Viaco part: V10-3620

On restart, the idle seemed better.

Previously, the idle would sometimes be very slightly "hesitant", so I'm wondering if the cracks were occasionally bleeding air into the intake system, perhaps fooling the computer into over enthusiastically actuating the N80 solenoid?
Only driven a few miles but no issues with N80 or Evap errors.

However, the car was so excited it at having so many new bits it blew the fuse to the 'leccy windows.

I'll update when the car has done more miles (or throws another wobbler).