Missfire at 5400-7500 rpm

[GTS-James]

when wide open throttle i have the odd missfire between 5400-7500 rpm, whats the most likely cause... injectors? fuel pump? its a stock rb26 boost restrictor removed.

[collector240sx]

Hi,

Have you had a look at your spark plugs lately. Might be worth a shot to have a look at
them, and to check the gaping while your there.

Before you get into the expensive stuff.

[GTS-James]

i have no tools! im living with a billet family in america right now it sux haha

[mitch32]

Probably coil packs, check spark plugs. In the US you can buy a socket set for like 40$ with everything you need. Go to Sears....

[natetheguy]

I have the same issue and I know it's not the spark plugs. I've changed mine a couple times and all were gapped to 0.8. My guess is a MAF is acting up. I haven't had a chance to test it on mine but I will let you know when I do.

[NismoS-tune]

I had this issue. Plugs. Another time it was 1 intermittent coil pack. Next time was another plug....

[nbsuperspiderman]

Could be a few issues. Check you plugs as stated above the move to your coilpacks. It could be you fuel pump or even your turbos. Without tools it is really going to suck though. I would start with the cheapest thing first

[Terrh]

I'd say plugs too, followed by coils. We don't have anywhere near enough information to figure this out though.

[GTS-James]

ya ill check the plugs when im home in 2 weeks

[Skym]

Higher rpm miss = sparkplug gap or heat range is incorrect. NGK PFR6A and 1.1mm should be factory for RB26. Should be NGK PFR7A with 0.8mm gap with intake, exhaust mods and a bit of boost added on top. If it has missed at higher rpm, then it can damage at least 2x coilpacks (from experience they were next to each other) but the rest of the coilpacks are usually ok. Grey tracking marks under mounting bracket on both sides tells you coilpack is leaking. Some dip in resin or use high temp silicon to fill the cracks on both sides, so coilpack stops leaking (temp fix).

I would pull the sparkplugs and read the tips. Then make decision on what engine needs. Heat range of sparkplugs can change due to cylinder temps changing. Leaning engine out via raising boost level can raise cylinder temps. If too hot with heat range, can melt the tip and widen the gap (from experience with running too hot sparkplug). If too cold, I think can blacken the tip. Should change heatrange every 75-100hp or if engine is running leaner (colder heatrange) or richer (hotter heatrange).

NGK website helps you with reading sparkplug tips and has photo's of what it looks like -

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp?mode=nml

Also helps you to understand heat ranges -

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp?mode=nml

Other interesting things to read about sparkplugs -

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/index.asp?mode=nml

[MaxGTST]

Check Coilpacks and MAFs before changing sparkplugs.. very comon problem on skylines.

[DarkCaporaL]

^ ?

Plugs are cheap it should always be the first thing you check. He should start by regapping his plugs. Then if that doesn't work move down to coilpacks, etc.

Plus the high RPM missfire is a 99% probability of a plug gap issue.

[NismoS-tune]

So someone with 1.4 bar should run what? heat range 7 with .8mm gap?

[Skym]

Look at hp level from stock (around 311hp stock for R32GTR, not 280hp). Every 75-100hp go one heat range colder. Then fine tune heatrange via reading tips with hotter if you run engine rich or colder if you run engine leaner.

Also environment plays a role, as colder environment = engine runs richer on warmup tables, so hotter sparkplug is used.