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BauerRacer

Seat Mii running lean

I have a bit of a head-scratcher here. My 2015 Seat Mii with a gasoline engine is giving me grief. It's got 118449 km on the clock, and lately, it's been running way too lean. I'm getting reduced engine power, the check engine light is on, the engine is running rough, and it's jerking like crazy when I accelerate. I'm suspecting a defective fuel injector. Does that sound right?

Summary of the thread

A 2015 Seat Mii with 118,449 km is experiencing issues such as reduced engine power, a check engine light, rough running, and jerking during acceleration, indicating it is running lean. The initial suspicion is a defective fuel injector, which is confirmed after further investigation. The solution involves replacing the faulty fuel injector, resolving the issue and restoring the car's performance.

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4 comment(s)

emil_schmid1

Whoa, lean running is never good! If your Mii is jerking and the CEL's on, it definitely sounds like a fuel issue. Could be a dirty or failing fuel injector, like you suspect. But before you go swapping parts, have you checked your mass air flow sensor? A bad MAF can mess with the air-fuel ratio too. Also, what about the oxygen sensor after the catalytic converter? Is that working properly?

BauerRacer (community.author)

That's helpful. How would a faulty oxygen sensor cause the engine to run lean? I thought that was only there to check if the catalytic converter is working.

emil_schmid1

Okay, an O2 sensor after the cat can affect the air-fuel ratio because the ECU uses its readings to fine-tune the fuel mixture. If it's giving incorrect data, the ECU might think the engine is running rich and compensate by reducing fuel, causing it to run lean. But since you've got multiple symptoms pointing towards fuel delivery, the injector is the most likely culprit. I would take it to a shop and have them check the fuel pressure and injector spray pattern.

BauerRacer (community.author)

Thanks for your help! You were spot on. I took it to a mechanic, and after checking the fuel injectors, they confirmed that one was faulty. Had all of them replaced. Cost me 515€, but now the car runs like new again!

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SEAT

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MII