Possible Misfire, Looking for some advice

Discuss the RB20, RB25 and RB26 series engines.
G0atlif3
Posts: 4
Joined: Thu Mar 31, 2016 3:12 am
Car: 1990 R32 w/ S2 RB25DET Moderately Modified

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Hello!

This is my first post so be gentle. :ohno:

So i believe I'm experiencing a misfire based on the following information. BTW I'm running a S2 rb25.

The problem being that I'm only experiencing it at random cruise/light throttle position moments. i had parked the car over winter and was having some trouble before i put it away but decided i would deal with it in spring. i have pulled the plugs and checked the condition, not to bad but could use a change(buying them on Friday). when i pulled the plugs around a month ago i moved cyl 6 to 1 and the other 4 were randomly placed as they had negligible differences. it seemed to alleviate the problem, but now that i have put around 1500Km on the issue is starting again. here's whats happening. I drive around 20km to work one way and after the car hits NOT, randomly, it will bog while cruising on the highway. the afr's are all over the place(when it happens) and i can clearly hear the exhaust tone change to a rough burp or boging sound, as if one cylinder dropped off. if i let the throttle off and get back on it nothing changes but when i give it some extra fuel it usually takes a second or two to stop and return to normal. today this happened three times, yesterday once, and the day before not at all. assuming its cylinder 6 again does anyone have an idea what could be causing the rapid deterioration of the spark plug? could it be bad coil wires, bad fuel injectors, bad regulator. any real input on direction would be worth it.

Yes i have new coils, ngk bcp7 iridiums, running greedy intake, stock injectors, 255 pump, etc. fueling does not seem to be the problem as it runs well until this happens, i personally checked and cleaned all six injectors and put them back in the opposite order to see if that would help.

Basically i dont want to burn another set of plugs trying to figure out WTF. thanks in advance for whatever advice you all may provide


Shiro
Posts: 1
Joined: Thu May 12, 2016 9:40 pm
Car: 1992 R32 Nissan Skyline Gts-t

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Same problem.

Watching for advice but will post if I solve mine.

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lexcrob
Posts: 559
Joined: Mon Sep 22, 2008 7:38 pm
Car: I get a different ride faster than I could update this.
Location: Clarksville, TN

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The story was hard to follow with the time jumps and the wording. Im gonna try.

Go buy cheap copper nico recommended part number plugs. Your wasting money.

Closing the gaps helps rb20's ill assume rb25's have the same coils or very similar.

Rb20det factory coils are garbage "mostly because mine were always old id assume".

Ive had great experience with spitfire coils. Also the ford taurus waste fire conversion works well.

Your not supposed to adjust the gap on fancy plugs so platinum iridium what are out for rb's unless you got spitfire coils they don't care about the gap in fact you can increase it.

Add grounds to coil mounting bolts add some extra grounds to them and any ground for that matter.


All that said the last thing you said was burn up another set of plugs. Which are iridium which are supposed to have a service life of like 150,000 miles. If the gap in fact has grown bigger burning them up....

Your running to hot look to cooling system issues. Id assume they would be blistered. Look at a plug reading chart it helps me. Hell put a fresh set of coppers in do a rip down the street at wide open throttle shut it down immediately after the pull and yank the plugs. Thats the only way to "read" a spark plug it does work well ive found.

Your not running high enough octane maybe? I read some stuff on rb octane requirements like 95 octane factory but japans rating is slightly different im no chemist. Proby why Ive pulled apart 3 rb20det engines that had severe detonation marks on the pistons. Guys run 87 or 91 through them thinking close enough but the pistons ive seen say thats a big mistake.

The last thing ill add is that rb engines factory plug is a different length as far a protrusion into the chamber it is not made anymore to my knowledge. Again adding to the notorious problems with rb's and missfiring. That < applies to rb'20 specifically not sure how similar rb25 is on that.

Good luck! Rob


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