Caddy Diesel Performance Drop + Rough Idle Fix Guide

Had similar symptoms on a 2019 VW Transporter TDI. The rough idle and increased fuel consumption were identical issues, which turned out to be a faulty fuel filter heater connection. The fuel system was struggling to maintain proper pressure, leading to poor fuel efficiency and inconsistent engine performance. The connector pins were corroded, causing intermittent contact with the heater element. This affected cold start performance and overall engine behavior. The repair involved replacing the entire fuel filter housing assembly since the electrical connections are integrated. The job took about 2 hours as the technician needed to purge air from the fuel system after the repair. This is not a major repair but requires proper diagnostic equipment and expertise with diesel fuel systems. Worth noting that neglecting this issue can lead to more serious problems, including potential damage to the high-pressure fuel pump or injectors. Filter replacement and fuel system maintenance are essential for diesel engines to perform correctly. Best approach is finding a shop specializing in diesel engines, as they will have the right diagnostic tools and experience with these specific fuel heater issues.

Thanks for sharing your experience. Had exactly the same power loss and rough idle symptoms with my 2020 Caddy. Relieved to hear your fuel filter heater issue got resolved without major complications. Since this sounds identical to my problem and I am planning to get it fixed soon, would you mind sharing what the total repair cost was? Also curious if you experienced any other fuel line or engine stalling issues since the repair was done.

After taking my Transporter to a diesel specialist, the fuel filter heater problem was completely fixed. The repair cost came to 95€, which covered fixing a faulty cable connection to the heater element. Much cheaper than I initially feared. The engine has been running perfectly since the repair, no more cold start issues, stalling, or rough idle. Fuel consumption returned to normal levels and the power delivery is smooth again. Important to mention that no additional fuel system problems have occurred in the months following the fix. The specialist found the root cause quickly, just a damaged connector that was causing intermittent contact. They were right to focus on the electrical connection rather than replacing the entire fuel filter housing as originally suggested elsewhere. This targeted repair proved to be both effective and cost-efficient.

I finally took my Caddy to a diesel specialist last week based on the helpful advice here. The experience was completely different from my previous mechanic visits. They diagnosed the fuel filter heater issue within an hour and found a damaged wire connection, just like in your case. Total repair cost was 120€, slightly more than yours but still reasonable. The fix included cleaning the connector pins and replacing a section of the fuel line that showed early wear signs. The cold start problems disappeared immediately after the repair. Power is back to normal and the rough idle is completely gone. Fuel consumption has also dropped back to usual levels. Really glad I went ahead with this repair instead of waiting longer and risking more serious fuel system damage.