Nasty misfire!!!

[sumfatchin]

Hi all, first post.

ive got an R33 gtst and it seems to miss under full load from 5 to 6 grand, I had the coil packs repleace ($1400) bucks, but it still does it. ive had a boost controller fitted and a k&n pod filter. Currently running running roughly ten pounds boost. (but i dont have a boost gauge so can't be sure). Also have a 3inch exhaust system, except for the cat which is 2.5' hi flow.

Any ideas as to what the problem could be?

[Majanal]

Firstly check your spark plugs. How many kms has it done... has it had the timing belt and all that done... give it a good service and see if that helps.

If you running a standard ecu then you probably still have the boost cut enabled... which I think is set at 8 or 9psi (If somebody knows exactly then please let me know).

Try these first.

If that does not work then you might try a smaller gap sized plug... that worked for me.

[sumfatchin]

yeah ive still got the factory ecu. would that be it? how much to

change it?

[BelGarion]

im currently experiencing the same problem, it went away with new plugs, but it has since come back, i have done about 1000ks on the new plugs and when i removed the front 3, the first and the second plugs looked a bit used (black ring round it ect) the 3rd looked pretty much unused... no ring or marking..

it only happens when i go flat stick with more than .7 bar (10psi)

boost cut doesnt occour till something like 13 or 14 psi

[sumfatchin]

i had new plugs put in with the coil packs, but the problem has stayed.

its weird tho, cause if u lay down a small burnout , then do a 0-100 accelleration run, it wont miss.

[BelGarion]

ok 1 outta 6 plugs looks unused, perhaps im having an injector problem...... i dunno, looks like its time to go see a mechanic

[Majanal]

I had this problem with the stock ecu... got hold of a power fc and problem hasn't come back untill I put stock ecu back in to test something else. I don't know what it is... maybe fuel delivery from the ecu seeing as boost cut is apperently at .9bar (14psi). I did also change gap sizes to .8mm.

I would redcomend that you run stock boost untill a boost guage is installed. When I first installed my bleed valve (which I'm not using any more) I still had the boost guage sitting in the passenger seat nect to me... took it for a drive and it really flew. Installed the boost guage and was actually running 1.4Bar which is WAY too much. The factory boost guage didn't even make the 7+ line.

[YRL05S]

Dan you whinge like a bitch, how much did i charge you for that bleed valve? Yeah thats right nothing. Lesson learnt boost gauge first then bleed valve, it went good though didn't it?

Anyway i think you car is brushing the boost cut, back off the boost until you throw a proper gauge in and then there are several ways such as fuel/boost cut defenders (around $ 200) and various other modules to get around this problem. Or do a Dan and get a powerFC.

[Majanal]

Not Whinging Rhys... just giving experience... I actually thought it was quite funny and an interesting experience... ie. Learnt that stock boost gauge is shit and bleed valve (which I appreaciated and still must get back to you) was more sensitive in my car than yours. did go REALLY hard though!

[Cubes]

I had exactly the same problem.

It was a hairline fracture in the spark plugs porcelin.

I pulled them out 3 damn times and checked them and didn't see the crack. Mine literally looked like a small hair was stuck on it.. Hence Hairline fracture

[greygirl1976]

sounds like your engine is leaning out put a adjustable fuel reg in it i worked on a 33 with the same problem anyway u shouldnt boost up 32's or 33's without a frount mount coz the standed cooler is as useful as a pedal powered wheelchair

[BelGarion]

i got a pretty decent sized frontmount on my car.... 600x200x70

[adam 32]

leaning out at 10psi - no

cant boost skylines on std cooler - wrong

needs a fuel reg - wrong

its got to be something to do with ignition if you are in fact runnin 10psi. this means checking coil packs (done), spark plugs, and ignition module. however if the spark plugs are uneven in colour it may point to a blocked/clogged injector which isnt spraying enough fuel causing pinging, but youd hear that...

is it missing on idle and all the time, or only in high rpms? what gap have u got your plugs set to?

[Cubes]

On only 10psi it won't need an adj. fuel pressure reg.

The standard ic's are fine to run 10-11psi on the r33's and on the r32's around 12psi. I made 152rwkw on 12psi.

When going to a fmic i noticed ever so slightly more lag and that holding 3rd and fourth out didn't seem to feel as flat.