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Heyo... Ok so my RB25DET Skyline with nistune has seemed to develop a missfire every single time at 6000-6250rpm, I see it as a lean spike on the dyno graph and also hear the engine stumble... Ive tried richening and leaning the area as well as adding/removing timing to no avail... Im only running stock coil packs with 13psi which I know are not the best but im confused why it always misfires at exactly the same point? What could cause this...
For abit more background information I want to the drags a few weeks ago, before hand the engine never missed a beat... At some point during the night I noticed the car would misfire at idle every now and then randomly... Did a comp test afterwards just to give it a checkup and all cylinders were good and very close together...
whats your spark plugs gap at??
Just something to check while you are at it, we i used to find melted cam sensor wiring on some LS engines with aftermarket headers following some spirited driving, this used to cause a miss at the same rpm all the time.
hope it works out.
The stock coils are notorious for giving trouble so I wouldn't be at all surprised if that is your issue provided your spark plugs are in good condition and properly gapped. While it isn't always a bullet proof test, if I'm facing this sort of misfire and suspect the ignition system I'll try gapping the plugs a little tighter and see if it makes any difference. On a turbocharged engine running high boost (13 psi is definitely not what I would class as high btw) I'd be running the plugs with a gap as tight as 0.5 mm / 0.020" just as a bit of a guide. This is often much tighter than people expect to be able to get away with.
Normally you will see the misfire occur at peak cylinder pressure which is where the engine makes peak torque. This is when it's hardest for the spark to jump the plug gap. 6000 rpm is probably a fair way above peak torque with your engine though I'm guessing. You could test if the misfire is load related by trying it at a lower boost level (provided you can go lower) and seeing if that helps it rev through cleanly. The other alternative that is a problem on the Nissan engines that is more related to high rpm is the CAS. If you had a spare you could swap in and test then that would help narrow things down.