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New Spark Plugs= Missfire

camoo

By camoo,
in General Maintenance

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camoo Collaborator

camoo

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I have a 98 r34 gtt, 3"turbo back, FMIC, boost controller running 12psi.

while doing the 100k service, i took out its denso iridium IK20 plugs with a gap of 1.1

and replaced them with NGK bcpr6es gapped to .8

Now it misses at idle and a little when accelerating lightly up to 2000rmp, but is fine when driving normally and when hammering it.

I played around with the gapping and the smaller ther gap the worse it is, but even at 1.2, the miss at idle remains.

Its not running lean, ive checked coils, airflow meter and for any vacuum leaks, all that aside,

the miss dissapears when i put the iridiums back in....

Im stumped, my mechanic is stumped...

I know i could just run the iridiums, but there must be something causing this, and its driving me nuts....

Could it be injectors?

Any help please??

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updpsi Collaborator

updpsi

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just buy the stock plugs n gap them too .7 or.8, cheap as fu*k and will probs fix your problem n near last as long as iridium plugs- i think they are

BCPR6ES-11

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mad082 Grand Master

mad082

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put the old plugs back in. if the miss goes away then you no it's am issue with the plugs. if the issue stays then i think you will find that the issue is with the coils. may have been a bit dodgy before hand and in the process of changing the plugs the got damaged and now they are worse.

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camoo Collaborator

camoo

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Sounds like my issue i have just changed my injectors..

Sounds like its on 5 cylinders if you gently rev it..

yes thats what mine sounds like, did the injectors help?

just buy the stock plugs n gap them too .7 or.8, cheap as fu*k and will probs fix your problem n near last as long as iridium plugs- i think they are

BCPR6ES-11

tried that, didnt help

put the old plugs back in. if the miss goes away then you no it's am issue with the plugs. if the issue stays then i think you will find that the issue is with the coils. may have been a bit dodgy before hand and in the process of changing the plugs the got damaged and now they are worse.

tried that, different only iridiums make it go away, also swapped my coils witha new set to test, made no difference

Maybe you dislodged some crud and it dropped into one cylinder?

blew it all out with compressor before i removed plugs, and it goes away with iridium plugs

thanks though eveyone.... :s

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DVS JEZ Grand Master

DVS JEZ

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Is ur ecu tunable? Some skylines do this. Its like an intermittant lean pop at idle?

If it annoys u just richen up the idle a tiny bit or keep running the iridiums if thats what ur car likes.

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camoo Collaborator

camoo

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Is ur ecu tunable? Some skylines do this. Its like an intermittant lean pop at idle?

If it annoys u just richen up the idle a tiny bit or keep running the iridiums if thats what ur car likes.

as far as i am aware its still the standard ecu as it has the sticker/seal on it.

im the first oz owner too, i think they have to make sure the ecu is standard when going through compliance... unfortunately lol

and yes it sounds like a lean pop, but my tuner put it on the dyno and its still rich, runs safe allthrough the rev range with a smooth power curve.

:(

im ok with running iridiums... but still i really wanna know why its doing this.. is this common at all?

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DVS JEZ Grand Master

DVS JEZ

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Alot of skylines have lean pop at idle intermittantly.

I normally richen the idle until the popping stops.

Why it happens with certain plugs i honestly cant answer that.

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camoo Collaborator

camoo

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Alot of skylines have lean pop at idle intermittantly.

I normally richen the idle until the popping stops.

Why it happens with certain plugs i honestly cant answer that.

hmmm driving through the city today i can notice it while going slow.... very annoying....

and its already running rich...

ill put iridiums back in and see how it runs...

any more ideas though?

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The.Godfather Enthusiast

The.Godfather

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did you drop one of the plugs when fitting them? they are fragile things and can get damaged easily...

but yeah throw your old ones in, even if its one by one and see if the missfire at idle goes away.

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camoo Collaborator

camoo

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did you drop one of the plugs when fitting them? they are fragile things and can get damaged easily...

but yeah throw your old ones in, even if its one by one and see if the missfire at idle goes away.

na didnt drop any,and even then, i went and bout another set of the NGKs just to be sure.

Also tired replacing plugs 1 at a time, and untill its all iridium, it still misses....

cheers though..

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camoo Collaborator

camoo

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so im going to try the o2 sensor in the exhaust....

Not to sure if this will have to much of an affect but with my limited knowlede i believe this is a logical step...

Any one agree or not?

help???? lol

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camoo Collaborator

camoo

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NOTHING TO DO WITH THE O2 SENSOR!!!!!!

Standard Iridium plug is a (NGK) heat range 5, I believe. Try some BCPR5ES plugs, see what happens.

yeh is did nothing tring another o2 sensor, so good call...

i got some ngk iridiums to put in tomorrow, just annoying that everine else with this same angine and same mods can run standard copper plugs, yet mine wont...

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camoo Collaborator

camoo

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so i put in some ngk iridiums with a gap of .8

makes the miss alot better, but still dosnt completely solve the problem...

any ideas??

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