Cold Start Woes: GMC Sonoma Diesel Injector Issues

Had the same cold start problems on my 2010 GMC Canyon diesel. The rough idle and cold start problems turned out to be faulty injectors. The symptoms were identical, hard starting in cold weather and unstable idle for several minutes after startup. A proper injector test revealed two injectors were not atomizing fuel correctly. This caused inconsistent fuel delivery during cold starts when precise injection is most critical. The repair involved replacing the problematic injectors and performing a full injector cleaning service on the remaining ones. This is considered a serious issue since faulty injectors can lead to poor combustion, increased emissions, and potential engine damage if left untreated. The symptoms typically worsen over time as carbon deposits build up and injection patterns deteriorate further. For proper diagnosis, an injector balance test and leak-down test are essential. These will show if any injectors are performing outside specification. With 100k miles, its common for injectors to show wear, especially if maintenance intervals were stretched. Would strongly recommend having a complete fuel system diagnosis done, including checking rail pressure and return flow rates. These tests will definitively show if injectors are the root cause of the rough idle and starting issues.

Thanks for sharing your experience with the injector problems. The symptoms you described match exactly what I went through with my Sonoma. Finally got it fixed last month, but I was curious about the cost of your repair? Also wondering if youve had any other fuel system issues pop up since getting the injectors replaced? My mechanic mentioned the fuel rail might need attention soon too, so trying to plan ahead.

Had the faulty cold start injector replaced about 3 months ago and the engine is running perfectly now. The total repair cost was 515 Euro which covered both parts and labor. Since fixing the injection valve, cold starts have been smooth with no engine misfire or hard starting issues. The fuel delivery system has been working flawlessly since the repair. My mechanic performed a thorough injector test on the remaining injectors and confirmed they were still within spec. This preventive check gave me peace of mind about the overall fuel system health. Regarding your mechanic mentioning the fuel rail, its smart to keep an eye on it, but dont rush into repairs unless tests show actual problems. In my case, the single faulty injector was the only issue causing the cold start problems. Sometimes replacing one component is all thats needed to restore proper function. Keep monitoring how it runs, but if the current repair fixed your starting issues, you might not need additional work right away. Just maintain regular service intervals to prevent future fuel system complications.

I took your advice and finally got my Sonoma looked at by a new mechanic who specializes in diesel injection systems. The injector test confirmed what we suspected, two injectors were shot and causing the rough idle during cold starts. Total bill came to 780 Euro for replacing both injectors, including labor and a complete fuel system cleaning. The repair process took about 6 hours since they had to remove quite a bit to access the injectors properly. They also checked the fuel rail pressure while everything was apart and confirmed it was still good. The engine fires up instantly now, even in cold weather, and runs smooth from the start. Its been three weeks since the fix and no issues with cold starts or engine misfire problems anymore. Really glad I didnt wait any longer as the mechanic showed me how badly worn the old injectors were. Definitely worth finding a shop that knows diesel systems and can do proper diagnostic testing.