Jeep Commander: Rough Idle Points to Misfiring Issues

I had a similar issue with my 2011 Jeep Grand Cherokee last winter. Having some experience working on cars, I first thought it was a spark plug issue, but it turned out the problem was more complex. The symptoms matched yours exactly, rough idle, jerking during acceleration, and drop in power. After the initial diagnosis, my mechanic found a defective fuel injector that was causing irregular fuel delivery to one of the cylinders. The faulty injector was creating an imbalanced air-fuel mixture, leading to the rough running condition. The total repair cost was 515 Euro, which included: Diagnostic testing, Replacement fuel injector, Labor costs, System cleaning and testing The repair completely resolved the rough idle and restored normal power delivery. The engine has been running smoothly since then. Before suggesting specific fixes for your Commander, it would help to know: Current mileage, Any recent maintenance history, Whether the check engine light shows any specific error codes, If the problem gets worse in wet weather, Whether fuel consumption has increased These details would help determine if your issue is also injector-related or potentially something else like ignition coils or fuel pump problems.

Last service was at 55000 KM and my current mileage is 57071 KM. Thanks for sharing your experience. Based on the symptoms you described, I am now more convinced I am dealing with a combustion misfire. The engine misfiring seems to follow the same pattern you mentioned with the imbalanced fuel mixture. The rough idle is particularly noticeable after cold starts. I will get the check engine light codes read first before proceeding with any repairs. Your repair cost breakdown is very helpful for budgeting purposes. I noticed my fuel consumption has indeed increased over the past month, which aligns with your injector theory.

Based on your mileage and symptoms, it does sound very similar to what I experienced. Since my repair, I have been monitoring the fuel consumption closely, and it returned to normal after fixing the faulty injector. Getting the check engine light codes read is definitely the right first step. Just to add to my previous experience, after the repair was completed, my mechanic found that the combustion misfire had actually caused some carbon buildup in the affected cylinder. They recommended a fuel system cleaning service, which I did, and it helped prevent the engine misfiring from recurring. A useful tip: when you get the codes read, if they show P0300 series codes, this typically confirms cylinder-specific misfires. My Jeep showed P0303, pointing to cylinder 3, which helped narrow down the problematic fuel injector. The rough idle after cold starts was exactly what I dealt with. Until you can get it repaired, try letting the engine warm up for a minute before driving, this helped reduce the severity of the symptoms in my case. Keep in mind that the spark plugs could also be contributing to the issue. During my repair, we found that while the injector was the main problem, the spark plugs were also showing wear and needed replacement ahead of schedule.

Thanks everyone for the detailed responses. I will have the codes read tomorrow and let the mechanic know about the potential fuel injector and spark plug concerns. Good point about the carbon buildup, I will ask about the fuel system cleaning service too since the throttle response has been sluggish. Looking at the symptoms again, everything points to a combustion misfire caused by either the injector or ignition coil. I will budget around 600 Euro for the full repair including diagnostics and cleaning. The tip about warm-up time is especially helpful since the cold start issues have been pretty bad lately. Will update once I get the codes and know exactly what needs fixing. I appreciate all the specific details about the P0300 codes too, that will help me better understand what the diagnostic results mean. Time to get this sorted before the engine misfiring causes any additional problems.