Posted to Technical Discussion Forum on 12/8/2012
Re: Ignition Current Waveform
I had an Altima like that last week with an intermittent
misfire that would only set a P0300 for some reason. It only
happened for short periods of time, but felt localized when
it happened, so I was able to isolate it with my Genisys
injector kill "special test". A coil swap and retest
isolated the defective coil. Why the PCM couldn't directly
identify the specific cylinder is a mystery to me.
I have experimented with Nissan COP primary circuits with my
Vantage Pro, in search of the cause of the dreaded P1320.
Certain COP Nissans and Infinitis are very sensitive to
primary ignition concerns, even on a "good-running" vehicle.
I have found that secondary issues like plug gaps etc. can
show up in the primary voltage waveform, and it's usually a
matter of scoping all of the primaries and investigating the
oddball(s) through swapping techniques.
Mr. Phelps makes a good point about warm-up catalyst
flakiness, which can cause spark plug and valve damage from
flying debris being aspirated under certain conditions. I've
seen it with my own eyes.
Take care, and keep on scopin'.
Quick Stop Smog & More
Sacramento, California, USA