The purge valve (N80) and the EVAP system cause a surprising number of GTI running complaints — the valve sticks and creates a vacuum leak or a fuel-trim problem.
Symptoms:
- Rough idle, stalling, or a lean code (P0171 / P2178) as a stuck-open purge valve pulls unmetered vapour.
- On turbo cars, a failed purge/check-valve can cause boost issues (blowing through a stuck valve).
- EVAP leak codes (P0442 / P0455) from the valve, the fuel cap, or a cracked charcoal-canister line.
The fix:
- Replace the N80 purge valve (cheap) — the updated part is the fix.
- For EVAP leaks, check the cap and lines and smoke-test the system.
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