Missfire (rb25)

[AFTDRK]

Hello there,

i got my car, a manual 1996 R33 gts25t, a month or so ago (imported)

my car had been missfiring at above 4500-5000 rpm when i received it out of compliance..

i thought it was due to having the wrong spark plugs (which were 1.1mil gap)

so i changed the spark plugs to .8mil NGK copper plugs, and that did fix the missfiring for about a week or so!...

and then a similar problem had surfaced again, the car at idle (when warm) sometimes has a heavy cough sorta missfire maybe once every 10 seconds or so

and feels a little bit sluggish driving around and then missfires on full throttle acceleration above 5000 towards redline (like the hesitating sorta missfire that having the wrong gap feels like) - my car has exhaust, decat, fmic, stock boost, air pod and bov blanking plate

i was thinking about removing the blanking plate and resetting the ecu.

or changing the spark plugs again...

Maybe i should try cleaning the AFM/TPS/Oxy Sensor or anything else like that?

Any ideas guys on what else it could be ?...

thanks in advance

Edited January 7, 2009 by AFTDRK

[JonnoHR31]

coilpacks

[Excess]

have you check your coilpacks?

[jeffboyracer]

+1 for coil packs

[geraus]

splitfires! got the exact same car! changed them! bang... problem miss-fire was gone.!

[Turbotonic]

try different spark plugs worked for me

[1SLP80]

As above, coil packs.

Is it a series 1?

I had the same issue, so i pulled out my coil packs and checked them out. I couldn't see any cracks in them, but i thought that while they are out i may as well give them a hit of silicone just in case.

So i covered all the coil packs with silicone, because even the most miniscule crack can cause drama's. let them cure for 24hrs and put them back in.

Went on the dyno just after and made 250rwhp and didnt miss a beat.

Remember to use high temp as well, i used shellys roof and gutter silicone if i remember correctly.

Here is a link to my thread like this on NS.com, their is pictures and other infomation you might find usefull.

http://www.skyline-gt.com/forums/index.php...327197&st=0

peace.

[MBS206]

Coil packs...

Go buy some split fires, and regap out to 1.1mm.

[DrewII]

hmmm i just finished diagnosing this problem. wasn't coil packs, spark plugs, dirty AAC valve

my AAC valve was leaking. loss of power and wrx sound. replaced AAC valve with second hand one. problem fixed. this "misfire" issue is so broad in the time iv been on these forums so many random reasons for it. try the top three first.

[bumble_bee]

i too got a second idle air control valve..

i always replace it..wen i clean my throttle-body..which is like every 3-4months..

or wen i notice my car is idling pretty pretty bad..

seem to fix the problem straight away...

but thats only far an idle issue..

for bad misfires around 4000-5500rpms..

wat fixes 33's with rb25det are..

u either got to replace the ecu..with an aftermarket one..lik power fc..etc..

or run a piggy-back..lik a afc..

im running a apexi neo afc..

seems to fix the problem...

its because of R&R's!!!!!!!!!!!!!!!!!

do a search..its a very very common problem on the rb25det...

some people say u got lean out the fuel about/around 4000rpms onwards..

becoz of the r&r that ecu does...

as for plugs..

get use to changing em..

coz rb25det kill plugs..

they dont burn oil or coolant...

they just kill plugs...lol

oh an another thing...

a aftermarket fuel pump..

it should also fix slight hesitation in the rpms..

so try an get one...

if u havent got one already...

wat mods have u got anyways??????????

hey MBS206..

so if u got spitfire coilpacks..

u reckon u should run a 1.1mm gap...

not re-gap them to .8mm?

is that correct?

[BoostdR]

I would put the BOV back to normal. Since new gapped plugs fixed the issue for a short time. Taking the BOV out of the loop causes mixtures to go very rich when backing of the gas and hench fouling new plugs very early. I wouldn't bother with splitfire coil packs if yours are working ok. They are not any better than perfect std items!