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Help Needed: Octavia VRS Misfire and Black Smoke Issues

Hi everyone! I'm reaching out for help with my Skoda Octavia 2011 VRS petrol. I've been experiencing persistent misfire issues. I've replaced the plugs, coils, PCV valve, purge valve, and related components. The car runs perfectly when the engine is cold, but once it warms up, it starts misfiring, idles roughly, and emits a lot of black smoke. Occasionally, the engine shuts off at traffic signals, and the revs take a long time to settle back to 900 rpm after revving. Despite these issues, there's no loss of power, and the fuel efficiency on motorways is unusually high at 60 mpg, which seems odd for a decat remapped petrol engine. Scans show random misfires and sometimes indicate issues with the engine temperature coolant sensors. Has anyone experienced similar problems? Could this be related to the injectors, ECU, or something else? Also, can anyone recommend a very good VAG specialist in southwest London? Thanks in advance for your help, and apologies for the lengthy post!

4 comment(s)

It sounds like you might be dealing with a faulty engine coolant temperature sensor, especially since scans have indicated issues with it. This sensor plays a crucial role in adjusting the air-fuel mixture based on engine temperature. If it's malfunctioning, it could cause the engine to run rich, leading to black smoke and misfires when warm. I recommend checking and possibly replacing the coolant temperature sensor. After doing this, please update us on the progress. If the issue persists, we can explore other possibilities. If you have any further questions, feel free to ask!

Quotation:
@CarlyMechanic wrote on
It sounds like you might be dealing with a faulty engine coolant temperature sensor, especially since scans have indicated issues with it. This sensor plays a crucial role in adjusting the air-fuel mixture based on engine temperature. If it's malfunctioning, it could cause the engine to run rich, leading to black smoke and misfires when warm. I recommend checking and possibly replacing the coolant temperature sensor. After doing this, please update us on the progress. If the issue persists, we can explore other possibilities. If you have any further questions, feel free to ask!

Just quick update about my car, after I replaced engine temperature coolant sensor drove about 20 miles faultless!

Quotation:
@Www888 wrote on
Just quick update about my car, after I replaced engine temperature coolant sensor drove about 20 miles faultless!

That's great to hear! It seems like replacing the engine coolant temperature sensor resolved the issue. If you notice any further problems or have any other questions, feel free to reach out. Safe driving!

Quotation:
@CarlyMechanic wrote on
That's great to hear! It seems like replacing the engine coolant temperature sensor resolved the issue. If you notice any further problems or have any other questions, feel free to reach out. Safe driving!

Thanks for support! Have a great day!

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