Misfire About 4000 Rpm

[gts25t4door]

hi all, I am having a problem with my series 1 R33 GTST. When I drive the car and rev the car slowly it wont missfire but when I put the foot down it will misfire at 4000 rpm.

So far I have changed the Spark plugs and I got my hand on a working set of coil packs so I swapped them, and now it is still doing the same thing. What I am asking is have people had a similar problem and what did they do to fix it? Could the ignitor couse this problem, could it be fuel pump considering that the continues along after the 4000 rpm mark?

I would normally take it to my Mechanic but I have a track day on Thursday and I cant fit it in by then, so any advice would be appreciated.

Cheers

Chris

[bikey]

hi all, I am having a problem with my series 1 R33 GTST. When I drive the car and rev the car slowly it wont missfire but when I put the foot down it will misfire at 4000 rpm.

So far I have changed the Spark plugs and I got my hand on a working set of coil packs so I swapped them, and now it is still doing the same thing. What I am asking is have people had a similar problem and what did they do to fix it? Could the ignitor couse this problem, could it be fuel pump considering that the continues along after the 4000 rpm mark?

I would normally take it to my Mechanic but I have a track day on Thursday and I cant fit it in by then, so any advice would be appreciated.

Cheers

Chris

what are the spark plugs you put in gapped at? try gapping them to 0.8, or if youve already tried this, 0.65. could solve your prob. theres heaps of threads on the topic as well.

[R31Nismoid]

Could be the wrong plugs

Dirty AFM

A connector corroded, or not connected correctly

Loose wiring somewhere

Fuel pump on deaths door

Poor pump voltage

etc etc (there are more, i just dont have time to type them)

These are all common problems and as bikey stated, there is a truck load of these types of threads.

Unfortunately there is no "one correct answer" for misfire issues.

Please have a search around and see what others have done.

Search using: Misfire

http://www.skylinesaustralia.com/forums/in...lite=%2Bmisfire

As you can see, there are lots of threads.

Cheers

[gts25t4door]

Yeah thanks guys, I have searched, and I think it might be somthing as easy as spark gap, but god knows what the problem is.

Thanks for the replys

[TTT]

if god knows.. he aint gonna tell you in a dream or nothing. try the fixes mentioned.

what spark plugs did you put in?

[Dose Pipe Sutututu]

miss firing at 4k?

sounds like a dodgey air flow meter... try disconnecting it and and starting up the car and see if there's any difference.. if there isn't the AFM is stuffed.

Or better yet, borrow your mate's AFM and see how you go.

Sounds like your ECU has gone into LIMP mode, see if the car is running rich and blow out black smoke at the back

[R32_GODZILLA]

I have the exact same problem. After changing my plugs with a brand new set with a smaller gap during a 5000k service by a reputable mech. and replacing coil packs with a set of working ones later down the track, i still get slight misfire at about 4000-4500rpm on full load - Now i've noticed it only happens during 1st + 2nd gear after the coil pack swap, not whilst in 3rd + 4th + 5th gear with WOT.

Pretty much in the exact same situation as yourself, as when i rev the car slowly, it's all fine throughout the rev range.

Keep me posted on how you go, as i'll try get to the bottom of this myself - I'll let you know if i get anywhere.

Cheers,

Steve.

EDIT - I have recently had an FMIC installed, amd the symptoms started a while after that + had bad plugs put in with huge gap (all replaced now though). Not sure whether this has anything to do with it, but maybe more charged air could be affecting the way the motor responds to it? Timing related maybe? I'll get her up on the dyno in a month or so time hopefully - see how i go.

[rick444]

I had exactly the same problem a few weeks back. I replaced my old iridium spark plugs with new NGK platinums, and the problem was fixed instantly.

[sh@un]

The fact that it happens under load basically at the revs when the engine is making peak torque should tell you it's a spark problem of some variety.

The charge density (air+fuel) is highest at this point, so any weaknesses in the ignition department will show up here.

[Nothing(V)an]

i had this problem 4 ages, bought normal plugs and gapped them, fixed it for about 2 days then became worse than b4 so i bought iridium plugs, havent had a single pop since. It's heaven

[r32woohoo]

http://www.skylinesaustralia.com/forums/in...p;#entry3134053

might be worthwhile to have a look at.

As i said in that thread as well, and what ive read in other threads, you probably have an air leak somewhere. Too much fuel + not enough air to ignite it properly

My leak was in the intercooler piping, one of the silicone joins were slightly loose and i didnt even realise.