Mate, Did a quick search for ya and found this.
Misfire under boost thread
http://www.skylinesaustralia.com/forums/in...?showtopic=1456
Anyway, I’ll post here so that it’s in one thread
Most common cause for the RB25det misfire/stutter/what ever you want to call it, at the 5000 – 5500rpm range is that it is at it’s maximum load.
This causes any small problems in the electrical system to show it’s head.
Things you can do on the cheap or even free are as follows:
1.) take out your coil packs and tape them up with electrical tape. Use quality tape, not the 6 for $2 type.
I did 3 tight layers.
When you take them out, you will see that from the actual COIL down towards the spark plug is a rubber boot.
I started at the base of the rubber boot (spark plug end) and wrapped the tape tightly all the way up to the coil and back down and back up. Each rotation goes HALF over the last one.
So 3 layers.. up, down, back up.
This prevents any hair line cracks that may be there from ARCING out any of the spark.
2.) spark plugs. If they are old, replace them with NGK BCPR6ES-8 (if they don’t have the -8’s you can also use the -11’s but will have to re-gap them)
Make sure they are gapped down to 0.8mm (you will need a feeler tool if you don’t already have one – they cost about $30 from what I can remember)
If your plugs are new or newish (I’d say spark plugs are only good for about 20,000kms) make sure they are gapped to 0.8mm.
Put the spark plugs in and tighten properly, put the newly taped coil packs back in.
3.) Take off your AFM (Air flow meter – it is bolted to your air filter box or pod filter if you have one of those)
Get a can of degreaser. Spray the INSIDE of the unit.. you will see a little knob in there with wires… make sure you spray them good.
Now rinse out under the tap (not too high pressure).
Repeat the above degreaser and wash step if not totally clean.
Once you rinse it, you will need to dry it.
I used a hair dryer on it till it was completely dry.
Put it back on your car and plug it all in.
Good to go.