Subaru Baja Rough Idle Fix: Cold Start Solutions

As someone with moderate experience working on Subarus, I dealt with very similar fuel injection issues on my 2005 Subaru Legacy. The symptoms you describe match exactly what I experienced, rough idle and hard starting, especially during cold start conditions. The engine misfire and cold start problems turned out to be a faulty fuel injector. The workshop performed multiple diagnostic tests on the fuel system, including: Fuel pressure testing, Injector spray pattern analysis, Electronic diagnostic scanning, Individual cylinder performance tests The faulty injector was causing incomplete fuel atomization, leading to poor combustion and rough running. Total repair cost was 515€ including parts, labor and diagnostic time. For a more accurate diagnosis, could you share: Check engine light status, any unusual sounds or vibrations? Does the problem improve once the engine warms up? Have you noticed increased fuel consumption? When was the last fuel system service done? This would help determine if your Baja is experiencing the same fuel system issues I encountered. The injector replacement completely resolved my cold start problems and restored normal engine operation.

Thanks for the detailed response on the injector issues. My check engine light has been on intermittently and the rough idle does improve once the engine warms up. Last service was at 164192 KM, when they changed the fuel filter but did not inspect the injectors. The engine definitely has a noticeable vibration during cold starts and I hear a slight hesitation when accelerating. Been burning through more fuel lately too, about 15% more than usual. Your experience with the fuel rail diagnostic tests is helpful. Sounds like I should have them do a full fuel system inspection and injector test to pinpoint which components are actually failing rather than just replacing parts out of nowhere.

Having gone through this exact scenario with my Legacy, your symptoms are textbook signs of fuel delivery problems, especially the increased fuel consumption and cold start vibrations. The fuel rail pressure test I had done was crucial in diagnosing my issue. The intermittent check engine light paired with rough idle matches my experience exactly. In my case, the workshop found that not only was the cold start injector failing, but debris in the fuel rail was partially blocking consistent fuel delivery to other injectors too. A comprehensive injector test showed three key issues in my case: Uneven spray patterns, Inconsistent fuel delivery at idle, Poor atomization during cold starts The complete fuel system service fixed it all: Full injector cleaning and testing, Fuel rail flush, New seals and filter Total cost was 680€ but solved both the rough idle and cold start problems completely. Given your identical symptoms and similar maintenance history, I strongly recommend getting the full diagnostic testing done rather than just replacing the cold start injector alone.

Thanks for the feedback. After reviewing the symptoms and comparing them to similar experiences, I scheduled an appointment to have the full fuel system diagnostics done. The matching cold start problems and fuel consumption issues mentioned definitely convinced me to get a proper injector test rather than just guessing. Will let you know what the fuel rail inspection reveals and whether my Baja needs the same comprehensive fuel delivery service that worked on the Legacy. The detailed explanation of the testing process helps me know what to expect and what questions to ask at the shop. The intermittent check engine light combined with rough idle and increased fuel usage really does point to injector problems. Better to find out exactly what is happening with proper diagnostics than waste money replacing unusual parts. Will update once I get the test results back.