Scenic Engine Running Rich

Whoa, that sounds familiar! My old Peugeot 307 (gasoline, similar age) had almost the exact same symptoms a few years back. Reduced power and the jerking – nightmare! I'd check your oxygen sensor readings too; a faulty O2 sensor can mess with the air-fuel ratio and cause a rich mixture. Also, when was the last time you changed your air filter? A blocked air filter can sometimes contribute to this problem as well. Just throwing some ideas out there based on my own frustrating experiences!

Thanks! The O2 sensor is a good shout. How would I go about checking the readings? Is that something I can do myself with a basic OBD2 scanner, or would I need more specialist equipment? Air filter was changed recently, so I hopefully ruled that one out.

Ok, air filter ruled out. Regarding the O2 sensor, a basic OBD2 scanner should give you live data readings for the sensor voltages. You're looking for anything wildly out of range or fluctuating erratically. Honestly, though, with all those symptoms pointing to a rich mixture and you suspecting the injectors, it might be worth biting the bullet and taking it to a workshop. They can do proper diagnostic tests and pinpoint the exact problem. I ended up chasing my tail for weeks with my Peugeot before finally admitting defeat and letting a pro sort it out!

Thanks a lot for the advice. I think you're right; I'm going to take it to a workshop. They confirmed it was a defective injector, just like I feared. Cost me 515€ to get it sorted, but at least the car is running smoothly again!