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.

We decided to then write a map for the car using our software as a comparison. Once installed the car was run again, and with the increase in boost over standard the misfire had returned.

Back to checking the plugs and coil packs, it was then evident that one of the plugs on the rear bank had suffered from cracking to the porcelain insulator (probably caused by being dropped previously or from being overtightened). This was causing the plug to breakdown under extreme load and caused the misfire. This explains why on the standard map the car ran fine, as boost pressure and load is less.

With a new set of plugs installed we tailored our ecu remap to the car and set it up. We then put the car back to standard and ran it to get a standard power figure. Finally we installed the map off the customer’s hand held unit and ran it to get a figure for this remap, and finally re-installed our own software and ran the car again.

We then had power and torque graps for the same car on standard map, remap from hand held unit and our own bespoke ecu software.

The graph below shows the results:

Colour Key:
:: Green = Standard Map
:: Blue = Generic Remap
:: Red = Courtenay Sport Bespoke ECU Remap and Set Up.

Needless to say with these results tested on the same dyno on the same day,  our customer opted to leave with our bespoke ecu remap installed.