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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!

Summary of the thread

A Skoda Octavia VRS owner experienced misfires, rough idling, black smoke, and engine shutdowns when warm, despite normal performance when cold. The issues were suspected to be related to the engine coolant temperature sensor, which affects the air-fuel mixture. After replacing the sensor, the car ran without faults, indicating the sensor was likely the cause of the problem.

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6 comment(s)

CarlyMechanic

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!

Www888 (community.author)

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community_author_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!

CarlyMechanic

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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!

Www888 (community.author)

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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!

Hi there! Unfortunately I have misfire issues 😱 Seems that misfires and black smoke out of exhaust in traffic and low revs, also check engine light on, after 2 or 3000 revs the engine act normal, and there’s no smoke at all….any advice would be appreciated, thanks

CarlyMechanic

community_quotation:

community_author_wrote_on

Hi there! Unfortunately I have misfire issues 😱 Seems that misfires and black smoke out of exhaust in traffic and low revs, also check engine light on, after 2 or 3000 revs the engine act normal, and there’s no smoke at all….any advice would be appreciated, thanks

Check for any vacuum leaks, as they can cause misfires and rough idling. Inspect hoses and connections for any signs of wear or damage. A vacuum leak can lead to an incorrect air-fuel mixture, causing the symptoms you're experiencing. Let us know how it goes or if you have further questions!

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SKODA

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OCTAVIA