VW Passat TDI Issues: Misfires & Rough Idle Problems

Had a similar issue with my VW Golf 2.0 TDI from 2014. As someone with moderate experience working on cars, I first thought it was related to the fuel system too, but it turned out to be a leak in the exhaust system that was causing irregular readings from the oxygen sensor. The symptoms were nearly identical, rough idle, jerky acceleration, and persistent check engine light. The workshop found that the exhaust leak was causing false readings, making the engine management system adjust the fuel mixture incorrectly. The complete repair, including parts and labor, cost me 265€. The fix involved: Complete inspection of the exhaust system, Replacement of damaged exhaust components, New oxygen sensor installation, System diagnostic check Before jumping to conclusions about fuel injectors, it would help to know: Have you noticed any exhaust smell in the cabin? Are there any visible signs of black soot around the exhaust components? What error codes are you getting specifically? Has the timing belt service been done according to schedule? These details would help determine if your issue matches what I experienced or if it might be something else entirely.

Thanks for the detailed reply. Latest service was done at 75000km, including a timing belt change. Getting error codes P0201 and P0202 consistently. No exhaust smell in the cabin and no visible soot. The rough idle and engine misfire seem to get worse when the engine is cold, especially during the first 5 minutes of operation. The fuel pump makes a slight whining noise which wasnt there before. The crankshaft sensor was replaced about 15000km ago, and spark plugs were done during the last service, so I dont think those are related to the current issues. Could really use some guidance on whether to check the injectors first or look elsewhere.

Based on those error codes (P0201 and P0202) and the symptoms youre describing, this is looking more like an injector issue than what I experienced with my exhaust system. The cold-start problems and whining fuel pump are additional red flags that werent present in my case. In my earlier VW Golf repairs, I learned that these TDI engines can be sensitive to fuel injector problems. The codes youre getting specifically point to cylinder 1 and 2 injector circuit malfunctions. Since youve already handled the timing belt and other maintenance items, I would focus on: 1. Getting the fuel pressure tested, that whining noise from the pump is concerning 2. Having the injectors electrically tested, could be a wiring issue 3. Checking the injector return flow rates The rough idle combined with cold-start issues often indicates clogged or failing injectors. My suggestion would be to have a proper injector diagnosis done before replacing parts. When I had injector work done on my Golf, the total cost for testing and replacing two injectors was around 800€. One thing to consider: since your oxygen sensor readings arent showing issues and theres no exhaust smell, we can probably rule out the exhaust system problems I initially had. The consistent error codes and symptoms point more clearly to the injection system this time.

Thanks for sharing those insights. After your response, I hooked up my OBD reader again and did some more testing. The P0201 and P0202 codes definitely align with what youre saying about the fuel injectors. The whining from the fuel pump is getting louder too, which makes me think the whole fuel delivery system needs checking. I called a few workshops and got quotes ranging from 750€ to 1100€ for full injector testing and replacement if needed. Most said they would start with a complete fuel system diagnosis including pressure testing, since the pump noise could indicate additional issues beyond just the injectors causing the engine misfire. Think I will book it in next week and have them do a thorough check of both the injectors and fuel pump. Would rather fix it properly now than risk more damage. Will ask them to inspect all cylinders while theyre at it, even though only two are showing error codes currently. Better safe than sorry with these kinds of fuel system issues.