Symptoms: P0302 cylinder #2 misfire code; obvious missing cylinder & rough running; AFR of 15-16 during cold start enrichment immediately after start on a 40F morning. Spark plug for #2 was grayish/whitish.

I have pulled the injectors and tested the resistance, all of them including #2 are at about 11.5 ohms, so the injector coil isn't dead.

This leads me to either a) the injector is clogged and physically unable to flow or b) the injector is not seeing voltage from the harness to fire.

Question: how do I test that ? (voltage from the harness to the injector). I'd like to do that before I send it off to Witchhunter to have it cleaned and tested. Is there an easy way without the special Mazda diag tools? That's what my service manual wants me to use. I could pull the fuel pump relay connector again and crank it, I suppose, but that will take two people.

 

I suppose you could swap the injector with another one, say number three, and see if the problem repeats in number three...
If it's still in two thee's a driver problem maybe?

 

I can swap injector positions. I've got time challenges this week, though, and was hoping to find a way to test it without reassembly of everything. It's only an hour to put together or take apart, but it adds up.

 

If you had access to a multi-channel scope, you could look at the waveform of the problem inj and compare it to a good one. If the waveforms are both good, it'd most likely be the injector.

I don't have a scope, I do things the ghetto-lishious way...
I want a hand-held scope...

 

Must have been a poor connection between the injector harness and injector #2. I swapped #1 and #2 injectors, and put dielectric grease on all of them. Car finally runs as it should. Before #2 shut down entirely I had been chasing a hesitation/stumble at 4500rpm with mid to heavy throttle. That's gone now as well.

 

Well, that works too! Lol...