Total MS noob and I'm just gonna go ahead and ask because I have midterms this week and cannot learn about my MS Pro until spring break next week.

I have a 01 Miata with that's basically stock and am dealing with a intermitten multiple random misfire code (p0300). From my research, it looks like it's my ignition coils BUT, heres the thing.. I just received a MSP PnP and am now wondering if I can plug it in just to see if I can test the fuel and ignition stuff and perhaps avoid wasting extra money. I have new spark plugs/wires and have changed the fuel filter. I think that leaves ignition coils, fuel pump, or injectors. I guess it's possible that the TPS or CAS is wonky but I am not getting any codes besides p0300. (I get the misfire when cruising and sometimes idle drop)

Please advise

 

Fix problems first, then deal with changing ECU.

 

Cause you guyz are wonderful humans?

Come to think of it, maybe it's not even spoon feedable?

 

Check your injector harness. I had a loose connection on #3 a few years ago that would cause the random misfire codes. It was clipped in, but didn't seat properly somehow.

 

Thanks for the tip, I'll go check now.

Not sure if it's a coincidence but I just got the code after fiddling with the tps plug.

I also caught it on my wideband.. After about 15 min of cruising, at very light throttle it feels like the car looses power. It makes kind of a brrrr sound. The AFR went from 14-15 to 16's. Even if I continue to push the gas with the same light pressure it feels like it has 20hp. If I mash the gas it moves forward again.

I don't know if the afr changed to 16's because the car went into some kind of limp mode or because there was not enough fuel.

 

AFR's of 16 means not enough fuel. Assuming you trust your wideband, an injector not firing will cause something like this.

In tunerstudio you can fire each injector with the car parked - do this. One of them may not fire, which will be your problem.

 

Thanks for the tip but I'm just wondering, let's say it's the coils going out and there's too much unburned fuel and causes a misfire, does the engine go into some kind of limp mode that is inherently a little lean? I just made a payment for some used coils with 55k miles on them for $55. I figure it's worth a try. If it's not fixed I'll hook up the MSP and see about the injectors before I change the tps and cas. If it's not the coils I hope it's the injectors because that would be a good excuse to get new ones

 

The oxygen sensor senses just that, oxygen. Any misfire whether rich lean or ignition related leaves unburned oxygen and results in a lean reading.

Dann

 

Ooooooohhhh!!!! Thanks!