Mercedes ML Hybrid Engine Performance Issue

Sounds like you're on the right track with the injection nozzle. A clogged injector can definitely cause those symptoms. Rough starts, higher fuel consumption, reduced power, and uneven idling are classic signs. The injection valve sprays fuel into the cylinder. If it's not spraying correctly due to clogging, the air-fuel mixture will be off, leading to those issues. Before you replace it, have you tried a fuel injector cleaner? Also, hybrid engines sometimes have unique injection systems. What error codes are you seeing?

I haven't tried a fuel injector cleaner yet, but I could. The error code is P0201 Injector Circuit Malfunction Cylinder 1. Could a simple cleaner really fix this, or am I just delaying the replacement? What cleaner do you recommend?

Code P0201 indicates a specific electrical issue with the injector circuit on cylinder 1, although the symptoms you describe could still be nozzle related. While a fuel injector cleaner might help if there's just a minor clog, the P0201 code suggests there might be more going on wiring, connector, or the injector itself is failing. A cleaner won't fix a bad electrical connection or a completely failed injector. Given the symptoms and the error code, I'd strongly advise getting it checked by a mechanic. They can properly diagnose if it's just a clog, a wiring issue, or if the injector needs replacing. Continuing to drive it with a faulty injector can cause further engine damage.

Thanks, I appreciate the advice. I took it to a workshop, and the injection nozzle on cylinder one was defective. They replaced it, and the repair cost 515€. The engine runs much smoother now, and the fuel consumption is back to normal.