Misfire?

Hey all ... can some body tell me wat happens when your car misfires ?
wat exactly happens ? cause when I step on it full ... it seems like it goes slower than when not going full out ... (my car is auto) well its probably faster but I think its actually SAME or only just a slightest bit faster .... is that misfiring ?

you will normally hear the diff
the only problem i have had with mine is (i think) the solenoid that changes the cam is stufed cause sometimews when i up my car it gets to 4500-5000 and it then breaksdown or flatspots for a little bit then keeps going
when mine does this it splutters and stays at 5000rpm or so ???

good luck with it

A series of loud pops/bangs from the exhaust in quick succession. You will also feel the car hesitate slightly, but not to the extent you've explained.

Minor misfiring can be just a small single pop.

What you've described sounds like a flat spot, which can be caused by lots of things :( Timing, plugs, fuel, sensors.

Need more details, what RPM?, any unusal noises?, does it improve (or come good) as the rev's climb, does it idle smoothly or pop & hunt?

yeah i think youre description is just a flat spot, which is exactly what i have on mine at the moment. Im getting an apexi S-afc fuel computer to try and rid this problem, because the R33 gts-t's over fuel a lot at high boosts, so as to stay away from pinging and detonation.

Misfiring is a definite pop and youll see black smoke coming out the back (which is unburnt fuel). You will only misfire if you have a serious problem with your car.

An incorrect plug gap (for the application) can cause misfiring, fouled plugs will do the same.

A combo of..... Standard gapped plugs (1.1mm), + a touch of fouling from rich mixtures, add in a touch of extra boost &..... pop pop pop!!!

Any one of these things "can" cause misfires, so too can extremely HOT coil packs, & sensor faults.

Very cool ambient air temps will show up misfire problems very quickly. You may find that on a cool night you get misfires @ high RPM/Boost, yet after 30mins driving it goes away, this is because (after 30mins driving) the plug tip has heated to a point that it burns the deposits off before it can cause a miss. Excessive amounts of octane boost "can" also contribute to the problems, as they coat the plug & foul it.

Gapping your plugs down (~0.9-0.8) will help stop most minor misfire hassles, or powering up your ignition system :D

thx for replies all ... well ... im getting some new plugs fitted today ...
and one more thing ... My car some times has trouble starting up ...
normally its like ... dadada woo ~~~ but some times its like ..dadadadadadadaddadadadadadadad wooo~~~~
you know wat i mean ... :rolleyes: so i changed the battery ... but it still some times does it ... so it was not the batteries ... and i have a major flat spot at high rpms... should i gap my plugs to .8 ? could the gaps cause flat spots ?

First the hard starting problem: Are you allowing the fuel pump time to prime b4 you start the car? or do you just turn the key to "start" straight away? Although it shouldn't matter, sometimes the pump needs to prime. Does the car run an aftermarket fuel press' reg & or pump?
Try waiting till the pump has finished priming, you'll hear it wurr into life when you turn the key to "on" (all warning/advisory lights on) wait till the pump's finished & then start the car. Start the car this way each time you drive it & see if it starts straight up every time?

Now for the flat spot: Does the car accelerate smoothly & quickly to ~4500-5000rpm & then drop away in power, only to come on strong again @ ~6000rpm to redline? Has the car been on a chassis dyno?, & if so, what's the power curve look like?
Gapping the plugs down to 0.8 will not help your flat spot problem (it may make it feel worse:() but it will help prevent misfires if you raise the boost level. More than likely the flat spot is a timing related issue (& fuel to a certain point), but without a good idea of exactly how the flat spot is occuring it's hard to say.

Flat spots & misfires are different things, a misfire is obvious due to the loud pop of unburnt fuel igniting, a flat spot is best descibed as a reduction in the rate of acceleration before peak power has been reached, seen as a dip in the power curve on a dyno run.

I'm NO expert on these issue by an means!!!, BUT... I have been through both problems in the past (with my car) I've had success on both counts, so hopefully I can steer you in the right direction :)

I just read another thread on your car problems.

What does you boost gauge show throughout the full rev range? (0-redline) Is it holding boost? I would have thought so, if you had a boost leak you'd hear it!!!

i will tell u ehn my boost guage finally gets here :)
been waiting for a month

whatsisname: thx for you top reply man ... the best one i got so far ... :eek: and .. oh yes to answer your Qs... yes I do have a after market press vac boost gauge ... analog autometer ...
and if I have a leak ... wat exactly should i be listening for ?
and throught out my whole rev range boost goes like this ...
well from 0 its 20 vac ... then ... step on the pedal slightly ... goes to say 10 vac ... then press pedal slightly more .. goes to 0 then press pedal lightly more goes to ... to 3 ... then to 5.... like goes up as much as i press down ... but then .. once it goes over this 5 psi barrier ... once i go above it ... it goes to 8-9 ... as in i cant get in stopped at 6 or 7 psi ... if you know wat i mean ... and yes the acceleration of my car ... from 0 ... if i step on it ... letting it go to around 3500 rpm ... i can dfinately feel some boost ... as in pulling ... but if I put my foot down full ... as in ... PUSH! and hard ... no difference in accereration then stepping like half or slightly more ... and at high ends ... i step on the pedal slight pull ... (duh) but if I go full out ... the car does seem to accerate faster but only slightly ... and I mean SLIGHTLY! like if I stepped on my pedal only slightly ... it would pull but reall barely any difference in pull ... its really frustrating when your car gets tired by going WHO!O!!O!!O!O!O!OOO!OO!O!OOOOO!O! but you get no accerelation .. i get the feeling im just pouring and wasting fuel ... not much difference in running car at 3500 rpm ...
well ... i hope this gives you enough info ... and yeah wat exactly was the problem with your last car ? and wat did you do and where did you do it ? and how much did it cost and how long did it tak e? :p
sorry with all the questions man ....
THx ...

I meant aftermarket fuel pressure regulator/fuel pump, not a boost/vac gauge :hehe: never mind :).

If you have a boost leak you'll hear a high pitched squeal when on boost, the higher the boost press' the louder it will get!!!

Hmmm, it's still a bit hard to give you a correct course of action based on your description :(

Your best bet would be to take the car into a knowledgeable local workshop (Skyline specialist would be best), take them for a drive & explain what the car is doing. Get them to put the car onto the dyno & then diagnose the problem? They "should" be able to either fix the problem or explain what needs to be done:) I can't suggest a workshop as I'm not sure where you live?

My "current" GTS25t had a flat spot @ ~5000rpm, this is a very common problem in the R33 GTS25t:( My car now has a smooth progressive power curve :), this is from custom ECU programming (via a Unichip), both timing / fuel map changes & static ignition timing adjustments.

Costs? - Varies, depending on the option taken, & brand. Interceptor units (Examples - Unichip / Apexi S-AFC & ITC) or full replacement ECU (Examples - Apexi Power FC / Link ECU).

Time? - 3-4hrs to a full day, depending on dyno time.

I hope you get it sorted out mate, then the car will put a smile on your face when you go WOT :)

thx once again ...
no i dont have an aftermarket fuel pump...
and ... well I when I boost i hear noise going up ... its sort of a wheeee!!!!!! but not HIGH HIGH pitched ... its high pitched ... like sory of wind sound ... but not HIGH HIGH so like 'oh no i cant stand it'
well I hope this all works out like you said ... and im sure it will put a smiile on my face when i kick my bros stocky auto WRX heheheh :smoker:

The induction noise (if you have a pod filter) will make a "wind sound" & so to will the turbo as it comes on boost (is on boost).

A boost leak is a very high pitched squealing noise, that "should" stand out as not quite right:(.

Goodluck with it mate, let us all know how you go?

if there is a leak where can it come from cause i may have one because sometimes i hear a high pitched noise like te ringing in yah ears after listening to loud music :)
but its normally only audable at a certain speed

how can i check if i have aleak

It'll be audible whenever you are on boost, although, if it's a very minor leak you may not hear it until your @ a certain boost pressure. As the boost increases so to will the squeal.

I had a FMIC pipe clamp not quite tightened enough once, all was fine until ~7+psi then I could hear (above the induction & usual turbo noise) the high pitched squeal I'm talking about. I checked & tightened all clamps/hoses on the pressurised side of the inlet until I found it.

Unless it a bloody huge leak!!! (in which case it'll be obvious) I doubt if the boost gauge will show a drop.

Check ALL pipes/clamps on the pressurised side of the inlet if you suspect a leak.

Of course, just because you can hear a squeal doesn't mean it's a boost leak, it could just be a squeeky BOV spring?