Hi, I have a 2001 BMW 318ti - it seems to backfire once the engine gets up to normal temperature, but is fine whilst the engine is cooli.e. just after starting it... Do you know what might be causing this? I think it might be a sensor?

Thanks

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW 3 Series (E36) Oxygen Sensor Replacement

i would inspect the crankcase breather valve. A backfire could be caused by ignition timing or a lean condition.

- Nick

Get a can of spray starting fluid and spray it around the intake manifold to look for vacuum leaks while the car is warm and running. Also examine the whole air path looking for cracks. My money is betting on the intake manifold gasket.