ylaw23 wrote: ↑Tue Jan 17, 2023 11:09 am
Hi, I am getting high idle revs just below 1500, no dashboard warnings, use lower gears when driving, and consuming a lot of fuel. Garages couldn't find the cause, they have checked the battery, cat converter, and it's not the cold weather, my car was normal last winter. Will have to take it to a VW dealer for a check. 2019 petrol tsi 95 se, low mileage aswell.
You may be able to save yourself the time and expense of going to the VW dealer as it sounds like your car could have been performing an active / forced petrol particulate filter (GPF) regeneration. Are there any messages under the ‘car settings’ menus accessed via the infotainment screen while your car is displaying high idle / high fuel consumption symptoms? - e.g. ‘engine needs to run longer’ or similar message? Was stop / start inactive? What types of journey do you normally drive? Low mileage could suggest a high proportion of your driving is on mainly short journeys.
If a high proportion of your driving is short journeys when the engine’s not getting up to normal operating temperature, then soot from the normal combustion process of your engine will collect in the GPF as the exhaust temperatures aren’t hot for the soot to be burned off passively. When the soot levels reach a certain level, the car will perform a forced / active GPF regeneration. If you’re driving mainly longer journeys and the engine gets up to optimum operating temperature, then the exhaust temperatures reach a high enough temperature to burn off any soot accumulations in the GPF passively and you’re unlikely to notice the regeneration happening.
There’s a separate discussion thread on GPF regeneration on the forum. From memory, most instances discussed in that thread are in relation to the GTI / GTI+ and typical symptoms of an active / forced regen are some or all of the following;
- increased engine idling speed
- slight lumpiness / hesitancy of the engine when moving off from rest and possibly a slight reluctance to accelerate
- significantly worse than normal fuel consumption
I’ve had one (I think) active / forced GPF regen in my GTI+ in the 28 months I’ve owned it and it took around 30 minutes to complete, and during that time, most of the above symptoms were present.
Link to discussion thread;
https://www.uk-polos.net/viewtopic.php?t=73177
If the engine is turned off before the regeneration has been completed the car will attempt to complete it during the next ignition cycle. Ideally, the engine shouldn’t be turned off during a GPF regeneration - hence the ‘engine needs to run longer’ (or similar message) under the ‘car settings’ and stop / start function not working. If the engine is turned off before a regeneration has been completed, the car will attempt to complete it during the next ignition cycle. Once the GPF regeneration has been successfully completed, things should be back to normal.