Seeking Advice for 2015 Fiat Siena Diesel Emitting Black Smoke, Showing Check Engine Light, and Experiencing Decreased Power Output and Increased Fuel Consumption

Hey there, Had a similar issue with my 2017 Fiat Punto Diesel, so probably can relate to your situation. Just to be clear, I'm not a professional mechanic, but I've got some experience dealing with car issues. In my case, the DPF was heavily clogged, caused by repeated short trips where the engine didn't get hot enough to burn off the soot in the DPF. Your symptoms sound very similar to what I had. I took my car to a trusted local workshop. The mechanics confirmed that the DPF was severely overloaded. I guess it's a common problem with diesel cars, especially if you're driving mostly in the city. They carried out a professional DPF cleaning process and it cost me around 1325€. It wasn't exactly cheap, but it definitely got my car back up and running smoothly. Mind, I'd recommend that you get your car to a good workshop ASAP and have them diagnose if the problem is indeed with the DPF. The sooner you get it sorted, the better. Could you please provide more specific information on how your car behaves? Especially when it starts showing the problems. Every detail might help diagnose the problem. It could also help in suggesting the next best steps. Hope this helps, and good luck!

Heya! Thanks for your quick response and sharing your experience, really appreciate it. At 117895 KM, my Fiat Siena Diesel was perfect until last week. Problems start when I accelerate too much, especially on the expressway. Initially, I just notice the drop in power output, then the black smoke and the rough running engine set in. Only once I slow down, everything goes back to its usual rhythm. But this isn't a one-time issue, it happens regularly, specifically during long rides. I'm mostly on city roads, so I guess your point about the DPF getting clogged due to short trips makes sense. I'll definitely take your advice and get it checked by a professional mechanic as soon as possible. I had a regular service last month, but seems like they did not catch this issue. Let's hope for the best, will keep you posted with the updates. Cheers!

Hey there, Glad my initial response was of some help. Your most recent description of the issue sounds all too familiar. The exact same sequence of events happened to my Punto as well, more power to your suspicion about the DPF. These Italian diesels are quite sensitive to short trips and city driving. When I had the DPF cleaned, it largely resolved these issues. The power was back, the black smoke disappeared, and smooth ride restored. You also mentioned you had a recent service, they should have ideally caught this, seems like a miss. Took me a two days in the workshop for the whole ordeal - diagnosis, cleaning, and getting the car back. Not too bad, just make sure you schedule your visit to minimize any inconvenience. Can't stress this enough, but the sooner you get this done, the better. Hoping your beloved Fiat Siena will be up and running in no time, looking forward to your positive updates. Good luck!

Hiya, I can't thank you enough for your thoughtful advice. Reading your experience is making me more confident about the DPF being the culprit. You're spot on about the recent service - they should've flagged this, it's definitely a miss. Great tip on scheduling the workshop visit, shall plan it accodingly to minimize disruption. Heading to the mechanic first thing in the morning, fingers crossed that the DPF clean-up brings my Fiat Siena Diesel back to life. Really grateful for your input it's been a lifesaver. I'll make sure to share how it all goes, hopefully with some good news! Take care and happy driving!