QX Diesel Woes: Power Loss & Rough Idle Mystery Solved

Hey there! I actually faced something really similar with my 2018 Infiniti Q50 diesel last year those symptoms sound very familiar! My car was doing the exact same dance: losing power, rough running, and that annoying black smoke. Turned out to be a leaky intake system. Took it to my regular workshop, and they found cracks in the intake manifold gasket that were causing air leaks. The whole repair, including parts and labor, set me back about 425 Euro. After fixing it, the car ran like new again. Before I share more details could you tell me how many miles/kilometers you've got on your QX? Also, have you noticed any specific times when these symptoms get worse (like when the engine's cold or under heavy acceleration)? Hope this helps get you started! Best, Mark

Thanks for the input, Mark! My QX's at 120741 KM and I just had it serviced last month. The symptoms you described are spot on it's definitely worse during acceleration, especially when I'm trying to overtake on the highway. The black smoke's particularly noticeable when I'm pushing it hard. Your experience with the intake manifold gasket sounds interesting I'll definitely get that checked out. Did you notice any particular warning signs before the gasket completely failed? I'm trying to figure out if I should take it to the dealer or find a good independent workshop. Cheers!

Hey again! Yeah, thinking back to my Q50's issues, I definitely noticed some warning signs before it got really bad. Started with a slight hesitation during acceleration, which I initially brushed off (big mistake!). Then gradually got worse over about 2-3 weeks until it became really noticeable especially that black smoke you mentioned during overtaking. My car had about 115000 KM when this happened, so pretty similar to yours. I initially took it to the dealer since it was still under extended warranty, but they wanted to keep it for ages and quoted a ridiculous price. Ended up going to my trusted independent mechanic who I've known for years. Quick tip from my experience get it checked ASAP. When my gasket started failing, it also affected the MAF sensor readings, which caused the ECU to mess up the fuel mixture (hence all that black smoke we both experienced). The longer you wait, the more strain you're putting on other components. One thing to check does your engine sound a bit louder than usual, especially at idle? That was another symptom I noticed but didn't connect the dots at first. Let me know if you need a recommendation for a good workshop in your area! -Mark

Thanks so much for all the detailed info, Mark! That's really helpful to know about the progression of symptoms you experienced. Yes, now that you mention it, I have noticed the engine running a bit louder at idle I hadn't made that connection before. Mine seems to be following almost the exact same pattern yours did, especially with how it's getting worse during highway driving. I think I'll take your advice and get it checked out right away. I'd rather deal with it now before it causes any additional problems with the sensors or fuel system. And yeah, if you know any reliable workshops in the Brisbane area, I'd really appreciate a recommendation! I'd prefer to avoid the dealer prices if possible. Really glad I asked here you've helped me understand what I might be dealing with. I'll update once I get it diagnosed and fixed. Thanks again!