As a Japanese vehicle specialist, this is something we don’t often see. So when we get a broken one in it was nice to throw all the diagnostic tools we had at our disposal at it!
A Honda Stepwagon, an imported vehicle with only about 75,000km on the clock, had come back to us after we had given it a full service about three weeks before. The customer's complaint was poor power and an engine light on and it was flashing. Often a flashing engine management light indicates a misfire. A global scan confirmed this and a code p0303 misfire on cylinder 3.
With new iridium plugs that we had fitted at the service and the customer had changed as well to try and rectify the misfire and a new cylinder 3 coil pack had not fixed the vehicle. We could hear the vehicle had a mechanical fault due to the sound when the vehicle turned over. A quick relative compression check quickly identified the problem - we did indeed have low compression on a cylinder. Next we wanted to identify which part of the engine was at fault. So with an amp clamp around the positive battery cable, a ditex pressure sensor put into the intake manifold and lastly cylinder 1 coil trigger, so I could identify which current ripple was from which cylinder.
Because of no compression on cylinder 3, the starter uses less current to turn over the engine and you can clearly see on the induction stroke we clearly did not have a negative pull of air from cylinder 3 before it comes up to the compression stroke. So without losing a single bolt on the vehicle, we could identify the internal fault and report back to the customer with our findings - he had a sealing issue with the intake valves on cylinder 3.
Unfortunately this vehicle is less than 2 months old and will be going back to the dealer who sold it to the customer to sort out the low compression on cylinder 3.