Suzuki Swift intermittant misfire

This car came in from another garage who had fitted plugs and coil packs but the fault remained.

The first thing to do was to confirm which cylinder the misfire was on.

With this confirmed we then have to find out whether it’s a fuel, ignition or a fault within the cylinder. The easiest place to start is with the ignition or spark.

A node light is fitted to the plug for the injector to see whether the light pulses with each injector pulse. As this was an intermittent fault at the time of testing it was ok.

We checked fuel pressure and it was also ok. We then put the car back to standard and used our pico scope to monitor the injection pulse whilst the car was running, pico scope is a great way to monitor electrical circuits whilst being non intrusive. The images are all recorded so you can leave the vehicle and if the fault happens whilst your away from the vehicle you can go back and see what happened

Whilst monitoring the injection pulse the signal would dissappear as if being switched off, seen here as a flat line

We then checked the integrity of the wiring from the injector to the ecu just to make sure there were no bad connections or chaffs in the wiring before contacting the customer to tell him that the ecu was at fault. An expensive component which you want to be certain of before swopping. With our experience and training in electrical diagnosis we were confident in telling the customer our results.