milakoehler1
Mistra rough running engine
Summary of the thread
A 2022 Hyundai Mistra with nearly 200,000 km was experiencing rough running, poor fuel economy, and acceleration issues, suspected to be due to a rich fuel mixture. Possible causes included a faulty injector or O2 sensors affecting the air-fuel ratio. After checking the air filter and considering injector issues, it was suggested to inspect the O2 sensors and injector waveforms. The problem was resolved by replacing a faulty injector and the O2 sensors, restoring the vehicle's performance.
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4 comment(s)
milakoehler1 (community.author)
O2 sensors, huh? I hadn't thought about those... I'll have to check those out. How can I check if the problem affects all cylinders? And where are the O2 sensors located exactly? What's the best way to check the injector waveforms?
mila_phoenix75
Figuring out which cylinders are affected could be tricky without proper diagnostic tools. Rough idle could give you a hint – try disconnecting each injector, one at a time, and listen for a change in engine behavior. As for the O2 sensors, there are usually two: one before the cat and one after. Access can be a pain depending on your exhaust setup. If you are asking that, I would recommend you to go to a trusted local workshop.
milakoehler1 (community.author)
Thanks for the tip about the O2 sensors and localizing the cylinder issue. I took it to the shop and you were spot on – turned out to be a faulty injector. Replaced the whole set and the O2 sensors. Cost me 515€, but she's purring like a kitten now! I really appreciate the help!
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HYUNDAI
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MISTRA
mila_phoenix75
Sounds familiar. I've got a Mistra too. Those symptoms scream rich mixture alright. Have you checked your O2 sensors? A faulty sensor can throw off the air-fuel ratio and cause the ECU to dump in extra fuel. Is it affecting all cylinders, or does it seem localized? Might be worth scoping the injector waveforms to see if one's acting up.