R32 GTR random misfire

[Spyglassmk2]

Hey what's up y'all, I'm new to the fourms but came on here due to frustration and a misfiring RB26. My 1992 Skyline GTR has a misfire that seems to be random. It does not happen upon could start from what I can tell. Checked the computer codes and they flashed all clear. I pulled the plugs and saw they were covered in black soot, some worse than others but all generally dirty. Replaced them with some iridium plugs from NGK gapped at .8, and that didn't fix it, then put some used but nice Splitfire coils on it, which seemed to maybe help a little but it could be placebo, also seemed to not wanna start with those coils in and low idle. The car is drivable but feels down on power and the misfire is pretty constant throughout the rev range. Only other thing I notice is she spits black smoke and it leaves these carbon specs all over the rear end. Maybe she's running too rich? I'm stumped and don't wanna put any money into it until I know what's wrong. Anyone have an idea? Thanks alot!

[GTSBoy]

2nd hand coils are not a diagnostic tool.

The other half of the ignition electronics is the igniter pack. It sits up on top of the motor getting cooked for 30 years.....it doesn't last forever.

The other other half is the coil pack wiring loom/connectors.

The other other other half is...how healthy is your alternator, battery voltage, when running?

The other other other half is that it could be a whole bunch of other things, from worn out CAS bearings, to an intercooler pipe/hose blown open (and hence running rich). But I would bet that the running rich shit is simply caused by the missing. If the fuel don't burn, because it wasn't lit, it looks rich.

[Ben C34]

1 hour ago, GTSBoy said:

If the fuel don't burn, because it wasn't lit, it looks rich.

It will smel rich, but read lean on a wideband though.

 

[Spyglassmk2]

1 hour ago, GTSBoy said:

2nd hand coils are not a diagnostic tool.

The other half of the ignition electronics is the igniter pack. It sits up on top of the motor getting cooked for 30 years.....it doesn't last forever.

The other other half is the coil pack wiring loom/connectors.

The other other other half is...how healthy is your alternator, battery voltage, when running?

The other other other half is that it could be a whole bunch of other things, from worn out CAS bearings, to an intercooler pipe/hose blown open (and hence running rich). But I would bet that the running rich shit is simply caused by the missing. If the fuel don't burn, because it wasn't lit, it looks rich.

Well that's my problem, I've done a lot of research but nothing really points to how I can test it to be sure. Voltage should be fine, is there any way I can pin point something like the harness or igniter before spending money on them? 

[GTSBoy]

Take to a mechanic that has a dyno so you can test it under load with gas analyser up the spout, and look for spitzensparks around the coils and pull coil plugs off to see which is missing and then swap stuff around to see if the miss follows the coil or stays with the cylinder. And then swap to known good coils and/or ignitor. Just the usual things.

There is nothing more frustrating than remote control misfire diagnosis. Nothing beats having someone who knows what they're lookign at actually look at it while it's running.