Mystery misfire
My 52-plate Skoda Octavia VRS with engine AUQ has developed an intermittent misfire. This occurs when accelerating reasonably hard using more than half throttle. Lift the throttle and reduce acceleration and the misfire disappears. At first, I thought it may be a spark plug or coil pack breaking down under load. The first time it happened fault code ‘16825 (P0441)’ was recorded, which is ‘EVAP Emission control system incorrect flow’. The second time, the code ‘17834 (P1426)’ was recorded. which is ‘EVAP purge valve open circuit’. Both codes indicate a possible faulty N80 purge valve. My question is, can a faulty purge valve cause a misfire or is it just coincidence that these codes are being produced?
Second, can you please confirm the cambelt replacement interval? I assumed it was four years or 60,000 miles, but two independent VAG specialists have stated eight years or 120,000 miles and say the four-year interval is for diesels only. Bryan Callaghan You have not mentioned the mileage of your Skoda or whether the spark plugs or coil packs were changed. It would normally be expected for a failing plug or coil pack to trigger a code with regard to the misfire, but it is not impossible for this to happen without a code being flagged. For that reason, if you’ve not already done so, I would check the spark plugs and change them if necessary.
Although the EVAP system can fail and will often give no symptoms when driving, it can also cause problems due to an effective manifold air Intake leak. This will cause issues with the air/fuel ratio and may result in hesitation. I have experienced symptoms very similar to those you describe due to a failed EVAP purge valve.
The data I have for the timing belt replacement on your vehicle is every 120,000 miles or 48 months, whichever comes first. I would always err on the side of caution when replacing the timing belt and do it sooner rather than later.