We were asked by a customer to diagnose a misfire on his Vectra VXR, which had occurred at around the same time as a set of spark plugs had been replaced.

Initially we checked which plugs were fitted in the front bank (as these are easy to check) and also to check the plug gap, which is critical on mapped cars. At this point all seemed well as the plugs were iridium ones, and they were correctly gapped.

Running the car on the rolling road (with full datalogging facilities) the car did indeed have a misfire running the ecu remap that was installed. As the plugs seemed fine, wondering if software had anything to do with the misfire we mapped back to standard (as the customer had brought his hand held unit with him) and ran the car again. The misfire had gone.

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