Lou2

Hi all, Been having this issue with my Octy estate (2011, 1.6 MPI) for the last year or so (ridiculous, I know). The car starts and drives perfectly fine (never any lights) for the first ~30 minutes or so, but eventually (usually on the motorway) I'll get a huge loss of power followed by an ESC light and a check engine light. The car is still driveable, just super slow - we're talking flooring it in 5th gear to maintain ~65mph on a flat road. Strangely, the check engine light will come on and off as you're driving, and the engine power will be restored once the check engine light is off (ESC always stays on). Sometimes the engine light will stay off, and the car will drive fine for an hour. Sometimes it refuses to turn off, and I'll have to drive very passively for a while. Pretty consistently, after ~3 hours of driving, the ESC light goes off and the check engine light stays on, but the car drives perfectly fine for the remainder of the drive. Since my commute to work is only 15–20 minutes, I can go week/months without this being an issue, although I just drove Edinburgh → London and back so I had to battle the car for the best part of a thousand miles. Garage has had a look, they changed the spark plugs and ignition coils, to no avail. I've also seen a few people fix this by putting fuel cleaner through the system, but this didn't do anything for me. I'll list a few miscellaneous trends that seem to occur with the issue, hopefully someone can connect the dots better than I can. If the car hasn't been driven recently, I can usually do an hours drive perfectly fine. However, starting the return drive, the issue will arise after almost exactly 15 minutes (regardless of motorway or urban driving). No lights are ever present when starting the car and I can usually drive around the city, or to work, without any issues arising. According to the cars MPG reading in the gauge cluster: flooring the car in 5th gear, 3k rpm gives ~15 MPG when no lights are present, however, during a loss of power event, it will read ~55 MPG and I will barely accelerate. Not sure if this could indicate an accelerator pedal issue, or perhaps something to do with the injection system or maybe the ECU isn't opening the IAC valve properly? The reading could be completely wrong though. The issue mostly arises when driving on the motorway in 5th gear. Sometimes, I can get the power back by downshifting to 4th (removing the light for some reason), or by sticking the car in neutral and coasting for 20 seconds before the light goes off. These solutions only work some of the time. Sometimes the car will 'kangaroo' due to the engine rapidly switching between giving normal power and low power when driving with my foot down with a check engine light on; although I'll normally come off the gas when this happens because I imagine it's awful for the car. Any help would be greatly appreciated. I'm completely broke atm, so it would be lovely if I could get in there and have a bash at fixing it myself (within reason haha). Thanks, Louis