having a minor problem with my FD, maybe someone here can help.


WOT + 2nd turbo (anytime after about 4300RPM, and especially during transition) I get a misfire SOMETIMES. not always, but sometimes. It almost feels like ignition breakup or something.

I just changed the plugs and wires (WHAT THE FUCK IS WITH T1 WIRE, WHAT THE HELL WERE THEY THINKING?!?!?!?!???), so I don't think it's anything to do with them, since it did it before I changed them, allthough it does seem to have gotten worse after. Wires are MSD 8.5mm, plugs are standard NGK 7/9's.

car is basically stock aside from intake and exhaust mods. Still has airpump and has a cat (though that's coming out in a few days)

Stuff I changed when I last worked on it: Changed plugs/wires, installed a catalitic converter, installed a new universal O2 sensor. And like I said, I think it may have gotten worse after I did that.

still have your old stuff?

try swapping in the old components one by one to isolate the problem.

Man, this kind of thing is very hard to troubleshoot without proper datalogs.

I guess you might be able to use your O2 sensor to help you:

Stick a + probe from an analog voltage gauge on your pathetic universal O2 sensor's line (It's a 1v signal) and the - side on the ECU ground. All it's going to tell you is if you're rich, lean, or stoic.

But thats good, because if that needle twitches hard to the lean side you can be pretty sure it's a fuel issue. If it twitches hard to the rich side, it indicates a PROBABLE problem with ignition.

unfortunatly, no megasquirt on the FD... not yet anyways.

Think the O2 would really indicate much?

Say it's a spark issue... poor combustion = lots of air gets into the exhaust = lean reading?

well, the old O2 sensor was busted, one plug wire I had to destroy to remove, and the old plugs were crap too... :P

sI'd start by going to the mazda dealership and getting stock wires. I've never found an aftermarket set that worked well.

Say it's a spark issue... poor combustion = lots of air gets into the exhaust = lean reading?

No, if you have poor combustion, none of the fuel will have been burned, and you'll get an incredibly rich reading.

O2 sensor doesn't read amount of fuel, it reads amount of air.

No fuel getting burnt = full load of air goes to the exhaust = lean reading.

Well, not air, %O2 in the air:P

O2 sensor doesn't read amount of fuel, it reads amount of air.

No fuel getting burnt = full load of air goes to the exhaust = lean reading.

on most cars with o2 sensors, the car operates on open loop at WOT, meaning it doesn't read from the o2. so if you get hesitation when you floor it, its probably not an o2 sensor problem.

NOBODY was saying it was an O2 sensor problem :P

However, I was suggesting he might use it for diagnostic purposes.

oh yeah. :)

<3


anyways, the issue seems to have fixed itself, as the car is running perfect now.

YAY.