BMW 5 Diesel Cold Start Issues: Fuel Heater Problems?

Hey there! I have some experience working on cars and had a pretty similar issue with my 2011 BMW 3 Series diesel last winter. The symptoms you're describing sound very familiar. I took my car to my trusted workshop when it started showing the same signs, hard starts, poor performance, and that annoying rough idle. Turned out it was indeed a faulty connection in the fuel heater wiring harness. The mechanic found a damaged plug that was causing intermittent connection issues. Total repair cost was 95 Euro to replace the connector and secure the wiring properly. Car's been running like a charm since then. Before we jump to conclusions though, could you share your car's mileage and whether you've noticed any warning lights? Also, when was the last time you had the fuel filter changed? This info would help determine if you're dealing with the same problem I had.

Thanks for the reply! My car's at 183704 KM and just had its service last month. No warning lights on the dash, but I'm definitely getting those same symptoms you mentioned. I'll have my mechanic check the fuel heater wiring, sounds like it could be the same issue. Did your car also take longer than usual to warm up when you had this problem? Mine seems to take forever lately.

Hey again! Yes, absolutely, my BMW had the exact same slow warm-up issue you're describing. Now that you mention your mileage and recent service, I'm even more convinced it's the same problem I dealt with. During the colder months before I got it fixed, my car would take what felt like ages to reach normal operating temperature. The slow warm-up was particularly noticeable when the temperature dropped below freezing. It was really frustrating, especially during those early morning starts. Just a heads up, when my mechanic diagnosed the problem, they found that the wiring harness had some corrosion build-up besides the damaged connector. Make sure your mechanic takes a good look at the entire fuel heater wiring system, not just the obvious connection points. The corrosion wasn't visible at first glance, but it was contributing to the intermittent connection issues. Since getting it fixed, my warm-up times are back to normal, and all those other symptoms, the rough idle, poor performance, high fuel consumption, they've all disappeared. Based on what you're describing, I'd bet good money you're dealing with the same issue. Let us know what your mechanic finds!

I really appreciate everyone's input! Based on what I'm hearing, especially about the similar slow warm-up issues and the wiring problems, I'm feeling pretty confident about what to tell my mechanic. It's such a relief to hear that this might be a relatively straightforward fix like it was with your BMW. Those symptoms you described match mine exactly, from the sluggish warm-up to the poor performance. I've already called my mechanic and booked the car in for next week. Asked them specifically to check the fuel heater wiring system and look for any corrosion, just like you suggested. Really hoping it'll be a simple wiring fix like yours was, rather than something more serious. Will definitely update everyone once I get it sorted. Thanks again for all the helpful advice, it's great having experienced BMW owners to bounce these issues off of!