I have a missfire on cylinder 3. I have swapped the coil from cylinder 6 and 3, but the missfire remains on cylinder 3.
I have also done the following: - replaced all spark plugs. - checked the wiring harness resistance all the way back to the controller.
I have access to a good scope and current probe.
The voltage waveform in the above shot is attenuated, but shows the noise involved.
Notes: - no DTC is set with the miss-fires - no miss-fire felt at idle (above shots are taken at idle). It is worst at about 1600 RPM in 6th gear. - This is a 2010 mazda CX9, it has dual spark ignition below 1500 rpm. - The Fuel injector on this cylinder was bad and replaced. - Intake manifold gasket was replaced. - intake was de-carboned.
Am I looking at a bad engine controller?