VW Fox Diesel Injection Failure Symptoms & Repair Help

Had similar issues with my 2002 VW Polo diesel. The symptoms you describe match exactly what happened, power loss, increased diesel consumption, stalling, and smoke under load. Turned out the fuel injector wiring harness had degraded, causing poor connections to the injectors. The faulty connection meant incorrect fuel delivery timing and quantity. This created incomplete combustion, leading to the smoke and power issues. The repair involved replacing the complete injector wiring loom and testing each injector connection. While checking, they found one injector was also damaged due to the electrical issues and needed replacement. This was a serious issue that required specialist diagnostic equipment to properly identify. Would strongly suggest finding a workshop that specializes in diesel injection systems, as general mechanics often lack the specific testing tools needed. The symptoms point clearly to an injection system fault, either electrical connections or the injectors themselves. Get it checked soon, as running with faulty injection can cause additional engine damage.

Thanks for sharing your experience. I had the exact same symptoms on my Fox last year. After diagnosis, it was the fuel injector rail that needed replacement along with two of the injectors that got damaged from the faulty rail pressure. The diesel injection system really needs proper diagnostic equipment to pinpoint the exact issue. Did you remember approximately how much you paid for the full repair? Also, has your engine been running smoothly since the fix, or have you noticed any other fuel system or performance issues? The reason I ask is because after my repair, I noticed the engine was much more responsive and the fuel consumption returned to normal, but I had to do some maintenance on the air filter system a few months later.

Just wanted to update on the costs and results since my previous reply. The repair came to 95€ for fixing a loose cable connection at the injection control unit. Much cheaper than expected, especially compared to your injector rail replacement. After the repair, the engine power returned completely and fuel consumption went back to normal levels. The diesel injection system has been working perfectly for over a year now. No air filter issues or any other problems have shown up since the fix. The diagnostic equipment really made the difference, the mechanic spotted the faulty connection right away and prevented any serious damage to the injectors. Running the engine with injection problems could have led to much costlier repairs if left unchecked. Your experience with the rail pressure issue sounds much more complex than what I dealt with. Good to hear your Fox is performing better now after the full repair.

Thanks for the helpful responses. Just wanted to share how my situation turned out. I took the Fox to a diesel specialist shop that multiple people recommended. Their diagnostic equipment quickly identified the problem, a failing injection pump that was causing irregular fuel delivery and damaging the system. The full repair ended up costing 780€ including parts and labor. They replaced the injection pump and cleaned the entire fuel system. The performance improvement was immediate, the engine runs smooth again with proper power delivery and normal fuel consumption. The mechanic also found some issues with the air intake that was restricting proper flow. A thorough maintenance of the air system was done while they had everything apart. This preventive work should help avoid future problems. Really glad I found a shop with proper diagnostic tools and diesel expertise. Regular maintenance checks will be important going forward to catch any issues early. The Fox now runs better than it has in years.