Toyota iQ Defective Injection Nozzle

Sounds familiar. Had a similar headache with my old Saab 9-3. Symptoms were almost identical – rough idle, poor fuel economy, the whole shebang. I was convinced it was the O2 sensor at first, but that didn't fix it. Are you getting any misfires, or is the exhaust smelling rich? It could be a clogged injector, like a blocked artery in your engine. Those tiny passages get gunked up over time.

Misfires, yes, especially when it's cold. And now that you mention it, the exhaust does smell a bit rich. So, are you saying it definitely turned out to be the fuel injectors on your Saab? How did you diagnose it for sure?

Yep, fuel injectors were the culprits. Ended up getting them cleaned and flow-tested. Made a world of difference. But honestly, with the mileage you're at, it might be time to replace them. Less hassle in the long run. If you're getting misfires and a rich smell, plus all the other symptoms, I'd say get it checked by a pro. They can do a proper diagnostic and confirm before you start throwing parts at it. My mechanic confirmed it with an OBD reader. It is never a good idea to start replacing parts without a definite diagnosis.

Thanks. Appreciate the input. Took it to the shop, and you nailed it – defective injection nozzle. They quoted me 515€ for the repair, which I've approved. New injectors are on the way. Hopefully, this will sort it out. I’ll post the result after the repair.