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Misfire/plugs/coilpacks

Noel

By Noel,
in Engines & Forced Induction

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Noel Community Regular

Noel

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Ok here is the story & YES i have read all the threads i could find on topic

I have a 97 s2 Gts-T

Mods are:

8.5psi (Turbotech)

R34SMIC

Pod

EVERYTHING else including exhaust is std

When i got car always had a slight pop on idle but never missed through rev range....anyway as i had changed g/box & diff oils, all filters etc since i go car i though id change the plugs as god knows how long they had been in there...got a set of iridiums heat range 6 (originals were 5) & threw them in...straight away it started to hesitate/miss at 4500-5000rpm so i did some research on here & regapped to 0.8mm & it made a hug difference but miss was still there on idle & in cold it would hesitate occasionally but i lived with it...then it started getting worse so i thought time for splitfires

whacked them in & presto miss gone on idle & no hestitation...but first time i drove it in colder weather at night its back???

Then I noticed when i give it a good kaning it tends to go away (as it does in the warmer weather) so im starting to think maybe going from a heat range 6 plug from 5 might be the whole problem as it seems when its cold they do not fire properly but when its warmer or after i drive it hard it seems to be fine

Maybe i should go back to a heat range 5 & my car is not modded enough to benefit from a heat range 6 plug & infact running worse

Any thoughts as im stumped?

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mad082 Grand Master

mad082

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you have said that they are 0.8mm gap but how old are the plugs? and what sort are they?

you shouldn't have to run the smaller gap with splitfires.

i would also suggest not running too much boost with the stock exhaust. it is a bit restrictive and will keep more heat in the turbo.

the reason why it goes away if you fang it is that the plugs are fouling. your o2 sensor may be a bit stuffed and causing you to run rich at low load which is fouling the plugs. then when you fang it the plugs are cleaning themselves.

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Noel Community Regular

Noel

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you have said that they are 0.8mm gap but how old are the plugs? and what sort are they?

NGK Iridiums & they are only 3months old

you shouldn't have to run the smaller gap with splitfires.

thats what i though hence why i am stumped

i would also suggest not running too much boost with the stock exhaust. it is a bit restrictive and will keep more heat in the turbo.

yea thats why im at 8.5psi & not 10-12psi

the reason why it goes away if you fang it is that the plugs are fouling. your o2 sensor may be a bit stuffed and causing you to run rich at low load which is fouling the plugs. then when you fang it the plugs are cleaning themselves.

but i get my usual km out of a tank? if o2 sensor was stuffed wouldn't that affect my kms per tank?

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mad082 Grand Master

mad082

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not if it was stuffed when you got the car. the hotter plugs you were running got to their self clean temp easier so they could burn the extra fuel easier.

and how many kms old are the plugs? not age sorry.

pull them out and have a look and have a look and see if they are fouled up (all black and sooty). if they are then it is running rich and it would be worth testing your o2 sensor.

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Noel Community Regular

Noel

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not if it was stuffed when you got the car. the hotter plugs you were running got to their self clean temp easier so they could burn the extra fuel easier.

and how many kms old are the plugs? not age sorry.

pull them out and have a look and have a look and see if they are fouled up (all black and sooty). if they are then it is running rich and it would be worth testing your o2 sensor.

ahh i see & does make sense

plugs done about 2000-3000k max

I heard o2 sensor should be changed at 60,000 anyhow? that true? if so im due for one as i just have passed 70,000

regardless i should change plugs yea?

THANKS

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mad082 Grand Master

mad082

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try changing the plugs to a set of copper ones (bcpr6es) and see if that makes a difference (they are only about $4 a plug, so won't break the bank). it also depends on if the o2 sensor was even changed when it was supposed to.

try disconnecting it and see if alters your fuel economy.

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Noel Community Regular

Noel

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try changing the plugs to a set of copper ones (bcpr6es) and see if that makes a difference (they are only about $4 a plug, so won't break the bank). it also depends on if the o2 sensor was even changed when it was supposed to.

try disconnecting it and see if alters your fuel economy.

cheers

what gap? the std 1.05mm or gap down to 0.8mm?

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Noel Community Regular

Noel

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Ok i think i may have gotten wrong iridiums originally & when i re-gapped i think i might have damaged the tips so i have a new set on the way which are already 0.8mm & i also have a new NTK o2 sensor on the way as it prob has never been changed (Thanks Kudos Motorsport) so will throw in new sensor & plugs when i receive & hopefully problem is solved....

if not i wont know what the hell it as i would have changed coilpacks, plugs, o2 sensor & would only really leave AFM or CAS in the equation

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  • 1 month later...
Noel Community Regular

Noel

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Ok so far i have done the following & miss at 5k is gone but i still have a bad miss at idle but mostly when its cold

Splitfires

New Iridiums 0.8mm

New o2 Sensor

What else could it be?

AFM?

CAS?

Idle Control Valve?

Cheers

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Richieb Collaborator

Richieb

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I was talking to a mechanic the other day, and he said you are better with "Normal" plugs.

We were discussing a similar problem with my drive at the time.

His opinion was that the Platinum ones, once they get a kicking, dont seem to recover, and need changing again... !!!

Makes me wonder why I am using them. at the price they are?!?

Now I am confused?!?!...., I thought they were the dogs goodies, but now...

Anyone else know better, and can substanciate it?, 'cos I'd love to know which way to go.!

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Richieb Collaborator

Richieb

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BTW, the flat spot on mine is at 5500 RPM. @14, 18 & 22 PSI (not using any more than 14PSI at the moment BTW!)... Kinda wrecked the 24PSI attempt for me that day!!

Mr Dyno said it was the coils, but I noticed a noisy Fuel Pump on Sunday eve, and someone said if it had been run dry, then it could have been damaged(it's about 250Km old now).

My thoughts are, if it was noisy, and a wavering noise was coming from it, there could be a problem, but the Dyno never picked up a lean situation, or any fuelling problem.

I am going to try the ones that Just Jap sell... the ones with 10% extra voltage. Seem a better price, and offer more spark too, I'll update when done.

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