BMW 7 Diesel: Cold Start Issues & Performance Mystery

Hey there! I had very similar issues with my 2020 BMW 5 Series diesel last winter. Started with rough cold starts and higher fuel consumption, then the check engine light came on. Turned out the fuel injectors were failing, which led to poor cylinder pressure and eventually damaged one of the glow plugs. The first symptoms were quite similar to yours, sluggish performance and struggling on cold starts. My mechanic found that the faulty injectors had been causing incomplete combustion, which then affected the glow plugs. It was quite a serious issue that needed immediate attention to prevent further engine damage. I'd strongly suggest getting it diagnosed at a specialist BMW workshop. These symptoms typically point to fuel delivery or injection problems in diesel engines, and waiting too long could lead to more expensive repairs down the line. My case needed new injectors and glow plugs, not a quick fix, but worth it to prevent bigger problems. If you're getting these symptoms, better to address it sooner rather than later. Best of luck.

Thanks for sharing your experience! That sounds exactly like what I'm dealing with. I'm curious, do you remember roughly how much the injector and glow plug replacement set you back? Also, have you had any other issues pop up since getting it fixed? I'm trying to budget for repairs and want to make sure I'm prepared for everything.

Hey again! Happy to share some good news! After my last reply, I took my 5 Series to my regular BMW specialist and turns out the cylinder pressure issue wasn't as bad as we initially thought. The fluctuations were actually a consequential error from a minor electronic glitch, so the fix was covered under warranty, didn't cost me a penny! Since getting it sorted, the car's been running like a dream. No more rough starts, fuel consumption is back to normal, and that sluggish feeling is completely gone. It's such a relief when these things turn out simpler than expected. Just to put your mind at ease, even though my initial repair with the injectors and glow plugs was pricey, it's held up perfectly. Haven't had a single issue in that department since getting it fixed. But definitely get yours checked soon, catching these things early usually saves money in the long run. Let me know how you get on with yours! Always interested to hear how these situations work out.

Thanks for the follow-up! Just got back from the mechanic today and wanted to update you. After hearing about your experience, I took it to a BMW specialist. The diagnostic showed it wasn't the injectors after all, turned out to be a clogged fuel filter and some dirty sensors. Much cheaper fix than I was worried about! The mechanic was great, really took the time to explain everything. He cleaned the sensors, replaced the fuel filter, and did a full system check. The whole thing cost way less than I'd budgeted for those injector repairs I was dreading. Car's running smoothly now, starts right up in the cold, and the check engine light's finally off. Really appreciate you sharing your story, it gave me the push I needed to get it checked out properly instead of putting it off. Feels good to have it sorted before it turned into something more serious!