A contest! What's causing the missfire?

[Duncan]

To save having to actually work out what the problem is myself, I thought I'd let all the guru's on here diagnose the problem

Symptoms

1) Car runs fine sometimes when flat out

2) Other times it missfires. Missfire can occur from 3000rpm right up to 7,200.

3) Engine check light has now come on three seperate times

The car

1) Is stock except for 9psi boost

2) May have been zooming around a track at the time

BTW, does anyone else have pretty rainbow patterns on their fuel rail?

[Nismodified]

Originally posted by Duncan

BTW, does anyone else have pretty rainbow patterns on their fuel rail? [/b]

perhaps the problem isnt with the car but the bad batch of LSD that you took?

[Driver]

Mine was doing this - i think it turned out my mechanic didnt tighten the spark plugs enuf

[Silver-Arrowz]

You bum! Have time to go to EC but no time to get your hands dirty! Pansy boy!

Take the plugs out and get some sand paper and lightly sand the top and see if that does the trick. If not then it's not your plugs.

[B-Man]

Small electrical problem most likely ..........conrod through the starter motor.

[Duncan]

plugs are under that big metal lid at the front of the car?

and I have witnesses to the pretty rainbow....

[fatz]

check youCAS maybe its loose and has moved a bit

happend to me once and i had the same symptoms

and for gods sake pull the ***n pugs out you girl

pete

[T0nyGTSt]

ringlands?

T.

[adam 32]

i had this, turned out to be faulty ECU. keep bringing up random sensor faults and would soemtimes put itself into limp-home mode.

[croat]

Duncan i have this same problem at the moment. I had new plugs in but changed them 2 days ago anyways to irriduim with .8mm gap. i have exhaust, cooler, boost to 9psi. When i 1st changed the plugs it worked well on 8-9 psi but after a big night cruising last night (gave it a bit!) and i put it up to 10 for a while then it began again... So i lowered boost back to 8 and now it does it non stop. i think its the coilovers, which is apparently a very expensive fix ($1000 and up).. keep me in touch if you hear anything new.

[OZ GTR35]

Duncan,

Sh!t man it could be any of those things. I personally over the last 4-5 years of owning a Skyline have seen the following cause problems with miss fire on my car.

My spark plugs, they were 10,000km old and drifted past 1.3mm. 1hr and $20 to fix.

My Air Flow meter, loose wire in AFM, 1hr to fix, $300 for a second hand one.

Dirty Inj, bad fuel in country NSW, 1hr work and a bottle of wine to my local workshop to use the ultrasonic cleaner and flow checker.

Coil pack not earthed properly, after changing my spark plugs I did not seat one of my DIY packs correctly. 1hr to fix and a kick in the ass for being stupid.

Reset ECU, the fuzzy logic can some times be a bad thing. 3-4 hours if you are at fatz house, hmmm beer.

Other problems I have seen from other members, fuel pressure / regulator, faulty spark packs, fuel pump. Never fixed em so can’t comment.

Personally start with the plugs as most the other issues produced more than a slight miss fire, it was more go / no go.

[Duncan]

Well, thanks to everyone that's replied, she's at the mechanic today (apparently they know how to open the big lid at the front and do stuff under it to fix things).

Keep voting, we should have an answer tonight.....

BTW, my vote was for alternator since it is intermittent.

[Sumo]

Spark plugs man, I did mine today... The coppers were rooted.

Exactly the same symptoms

Sumo

[HRthirtyone]

check all the earth wires that come off the loom near the fuel rail, make sure none are loose....

[TTT]

it will be spark related.

but because you said it is only sometimes, I will go with the coil packs.

My one started off that way, it would come and go...

at first it was just an occasional hicup, then it would miss for longer, then eventually that particular coilpack completely died.

this makes it easier to find..

bought a second hand one fo $40 problem solved..

the most annoying thing about it being an intermitent thing is that it makes it hard to find which coil pack it is..

[mist]

besides the coil packs, note that some of our skylines are pretty old - the electrical system is ancient. Perhaps an earthing/grounding kit may solve your problems..

[B-Man]

What ever it is , it must be still in the shop - went in of friday - now Sunday and no indication from Duncan yet.

So, prolly not plugs as that would have been done first, and Duncan would have his car back and have told us what it was.

Or , not.

I stick by my original analysis.

[Duncan]

:oops:

sorry b-man, yeah it is back but not driven yet. I told them your theory and they had a look, apparently all conrods are still within the block (not sure how they can tell tho :confused: )

They checked plugs (apparently they ARE under the bonnet!) and cleaned the AFM....but since it was always intermittent I'm not 100% sure its fixed.

[rb25]

so whats the answer?

[rb25]

is this a piss take?