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Q: Cylinder 1 misfire. Leads plugs and coils all changed. Is it the ECU or are there other possibilities?

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I suspect ECU as these are a common fault with Fiat Punto. The reason I have doubts is that the engine light has not come on. Surely if there is an ECU problem then the light would be on??
My car has an automatic transmission.

A: Hello, thanks for writing in. If you have a...

Hello, thanks for writing in. If you have a misfire on that cylinder with a new plug and coil then you either have an injector issue or an internal engine problem. Most of the time the problem is internal due to a bad valve seat. I usually do a compression test to see if the problem is internal. If it is then the cylinder head will need to come off and be rebuilt. If the compression is fine then the injector may be bad. If that tests fine then further testing of the wiring and the control module would need to be done. If you want to have this misfire checked out, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this.

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