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Missfiring problems...

BenA31

By BenA31,
in General Maintenance

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BenA31 Experienced

BenA31

Posted
Posted

well i've had a intermintint missfire in my car for quite awhile now and nearly coming to the point of not knowing what to check next, its also become quite hard to determine which cylinder it is. Diagnosing had become rather a big pain and am asking for help!!

so far i've, not all realating to fixing miss but could help....

changed engine loom wiring

changed CPU (currently got auto one, and manual car)

changed CAS

had injectors professionally cleaned and tested

changed AFM

replaced O2 sensor

cleaned ACC valve

checked cooler piping for leaks

done compression test with 10psi difference at the most

replaced coolant temp sensor

re wired coolant temp sensor

next thing i'm probally going to replace is the coil packs with some spitfire ones, but is there anything else that ive missed out on checking??????

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https://www.sau.com.au/forums/topic/47634-missfiring-problems/
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TurboX Mentor

TurboX

Posted
Posted

You did not say you changed the plugs but I guess that was a given? :Oops:

I know when I last had fitted iridium plugs and got MD to dyno my car he had to change back to platinums to get rid of misfiring. Even gave me back my $30 each investment :rofl:

rb25 Grand Master

rb25

Posted
Posted

My 33 started misfiring after i changed from coppers to platinums (still a 0.8 gap) and ran more boost and timing with the powerfc. I dont think the standard coil packs have much kick left in mine so im replacing them with spitfire's next week hopefully. I'll let you know how it goes. Oh, and as a temporary fix im using coppers gapped to 0.7, seems to have eliminated the misfire.

-rb25

BenA31 Experienced

BenA31

Posted
  • Author
Posted

yeah forgot to mention, i have replaced the spark plugs a few times now. i've tried platinums, iridiums, and now currently using coppers, gapped to 0.7 i think.

i'll probally try swaping the ignitor soon with a mate. coil packs are gonna be changed no matter what as they have those little cracks on nearly all of them at the top, as mentioned in another thread that i've read awhile ago.

Zahos Mentor

Zahos

Posted
Posted

Try this thread: http://www.skylinesaustralia.com/forums/sh...ead.php?t=32356

It has been the solution for many including myself.

If you talking about an RB25DET, then they are notorious for isfiring above 4500 RPM on higher than standard boost.

- a SAFC or PFC with mixtures leaned out to 12:1 will GREATLY help.

- copper plugs gapped at 0.8 (BCPR6E)

- and coils taped up like describd in the post above...

A SAFC fixed my problem, but the misfire came back recently...

I just finished taping up my coils, now the mis has completely gone...

Give it a go... it will only cost you 1-2 hours and a couple of $$ in tape...

BenA31 Experienced

BenA31

Posted
  • Author
Posted

thanks for the reply zahos, unfortunatlly, taping them up is really only a temporary fix. i have already done that, it helped slightly at high revs but its still got the intermintint miss at idle.

yeah you could possibly be right about the SAFC, it is running a bit rich, so maybe thats the issue. i'm gonna try get hold of a ignitor module today to swap if i can.......

BenA31 Experienced

BenA31

Posted
  • Author
Posted

it couldn't be running that rich to cause a miss surely?!?

its basically all stock cept for boost running at 10psi and the fuel pump, and 3" cat back-- that wouldn't cause that many issues would it with the fueling. thou i am getting only like 350km outa a tank but with a bit or hard driving that is...........

Zahos Mentor

Zahos

Posted
Posted

Mine was missing like crazy at around 4500-5500 rpm before I intalled and tuned my SAFC. With the SAFC tuned it was as smooth as a baby's arse!

I developed a miss again lately, but that b/c of the coil pack cracking.

Now with the coils taped up.... it's like a baby's arse again

BenA31 Experienced

BenA31

Posted
  • Author
Posted

thanks for the help so far guys.

Trust me, thats what it is, what year is your car?

When you boost it, it dumps more fuel in and floods the cylinders.

its a 89/90 R32 with a rb20det

the miss is mostly noticable at idle with it been a constant intermintant one. (like every 3-5 secs) thou is also noticable with the revs held up higher.

benm Grand Master

benm

Posted
Posted
When you boost it, it dumps more fuel in and floods the cylinders.
I've replaced my iridiums (which looked fine) with brand new coppers, taped all my coils but then replaced #1 + #4 which I believe are the fault 1's with 2nd coils and my problem has gone from 'missing' to now feeling like a few 'flat spots' under load on only 7psi so obviously I still have a coil issue but do you think my car is running rich enough to cause the missfires too ?

cam-afr.jpg

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