Misfire but not coilpacks.

[Kettle]

I have a very intermittent misfire going on. When it comes on, it lasts through the entire rev range and really makes the car feel like crap to drive. Sometimes it happens from when I first start the car, other times I can be driving for a while and then it starts. Doesn't matter if it is hot or cold weather either.
The car is a 1992 R32 GTR. The ECU is throwing up an error code 21, ignition system. I know these cars have a habit of coilpacks breaking down so I replaced them with new ones. Sadly that didn't fix it so I replaced the coilpack wiring loom which was falling apart. This didn't fix it either. Next I replaced the ignition module which was a bit dodgy too and it still isn't fixed.
What else should I be looking for? This is driving me crazy!

[mcfly]

Check the coil pack harness, ignitor to coil pack wiring.

They get hard and brittle from the heat cycles and finally start to break down.

[Zacho]

He said he replaced that loom.

I would make 100% sure you have a good ground on that coil harness and that it is hooked up. The code 21 I believe is related specifically to the circuit. Since you have replaced everything from the ignitor and onwards, I would check your wiring before that.

Have you tried other spark plugs at all? The random-ness of this problem does make me think it is a wiring related issue.

[mcfly]

ah yeah, nevermind then.

ignitor was replaced with a new new one?

[bobbo]

I went through the same thing. The ignition module solved my problem. Out of curiosity what are your plugs gapped to?
Are you using a stock ecu? If you have a friendly Nissan dealer near by they can plug CONSULT into your car and kill each cylinder one at a time. This may help indicate atleast which cylinder is failing.
Good luck!

[Kettle]

Well I don't know what the problem was, but it appears that I have fixed it. I replaced the spark plugs on the weekend, the old plugs had a 6 heat rating and I replaced them with a 7. At the same time I made sure all of the connections were secure, made sure the ignitor was earthed properly and cleaned out some moisture that had gathered above one of the plugs. The car is running really nicely now, took it for a good sprint up the local mountain.

[bobbo]

Somewhere there is a vagina on each Skyline. It's the only way one could explain how tempermental they are!