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Discussion Starter #1
My car has developed a misfire under load and wont boost properly.Here is pics of my plugs and coil packs.





As you can see plug 4 seems to be darker than the rest. Possible coilpack problem? I have wrapped the rubbers of the coilpacks with insulating tape to see if will improve matters but its not improved. The base of rubber boot 5 also has some white deposit. Arcing? Also I noticed that the plugs are NGK PFR7A (11)? Is this the wrong grade of plug?Looks like a grade 7 with 1.1 gap. I will be changin them to BKR8EIX anyway because my car is Stage 1 running 1 Bar.
I also have a set of AFMs I am going to try but can it be that causing the problem?
Thanks Andy
 

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When I had similar I numbered the plugs (like you have) swapped the cylinder into which they went back, And swapped a couple of the coils, The plug in 6 still got messed up, Which suggests mine is burning oil on no 6 cylinder.

Yours looks like a spark problem though doesnt it ? Have you run a compression test ?
 

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Discussion Starter #3
I havent done a compression test yet. The dark plug looks more like a lack of spark and running rich than a burning oil problem.
 

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Low compression can cause it, it could also be a bad injector, its not oil your right, There arnt enough deposits. swap the plugs and coils about and see if the problem moves with a plug or coil...
 

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Discussion Starter #5
Yeh thanks Marky Ill give that a try. Im needing new plugs anyway. Those have seen better days I reckon.
 

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Do you coil packs smell after a run as that can indicate problems?
Very crude diagnosis i know but it may help.
 

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Discussion Starter #7
323ian - There are no smells.On inspection they are in excellent condtion. I reckon its a dodgey single coilpack or injector.
 

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Discussion Starter #8
I have changed the plugs to the correct NGK grade 8 0.8 gap and swapped the coilpack over from 4 to 1 and the plug is still getting fouled in number 4. Looks like an injector problem. On examination of number 4 injector i can turn it by hand?Loose? Help guys!
 

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I have changed the plugs to the correct NGK grade 8 0.8 gap and swapped the coilpack over from 4 to 1 and the plug is still getting fouled in number 4. Looks like an injector problem. On examination of number 4 injector i can turn it by hand?Loose? Help guys!
yeah that doesn't sound good. What injectors are you running - I just swapped my 444cc stockers for 700cc - 4 of them were bad but two are good - if you pay shipping you can have em for free...
 

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Discussion Starter #10 (Edited)
Hi you have PM. I have standard yellows 444cc yellows.Thanks

I have also done other checks. The car only has a small misfire from 1k onwards and worsens as the revs rise. Car starts and idles fine.
Pulled the coil plug on number 4 when running misses badly.
Pulled the plug on injector 4 misses just as bad.
This is driving me nuts! Anything else I can check?
 

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Had a similar prob on mine that only happened when warm under load i.e couldn't be solved by pulling plugs/coilpacks out at idle. VEry annoying...turned out to the ignition module. Only found out by borrowing Paul Cawson's and finding the car suddenly ran ok.

Still got a problem with dad;s R34 GTR. Very weird...runs fine but on a long journey sometimes it will decide to lose power with a misfire. Constant throttle at 80 and then suddenly starts missing...tiny bit more throttle and it clears and you can go back to previous throttle position. Weird thing is it only ever shows up after a prolonged motorway trip..i.e the car has been warmed for eons. Has done it before and after mapping by Abbey so no glitch there.
 

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Discussion Starter #12
Turboslippers thanks for that. I will need to borrow an ignition amp to test as well. Anyone local I can borrow theres for 10 min? Can a faulty one affect just the one coil pack?
 

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Oh yes....I got home once and it was missing as I warmed it down so I was 'delighted' to pop the bonnet and confirm by switching plugs/coilpacks. Number 3 was missing so I switched and it ran fine. Until it got back up to temp and then did it again. I think i switched 3 coil packs and played around for hours before the ignition module suddenly cured all the problems
 

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Discussion Starter #14
Thanks a lot mate. I had even ordered a set of coilpacks too.Ill see if I can borrow one to try or even buy one.Cheers.
 

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If you can borrow one of a fellow skyline owner them this could save a load of grief. Ok, might me nothing to do with it but if you can borrow one for a brief spin then at least you can rule it out or not. I was kicking myself after I found out what it was...
 

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Discussion Starter #16
Ok you have given me hope. :bowdown1: Ive been tearing my hair out all week. New plugs, cleaned up afms, reset ECU, checked injectors etc.
All injectors are clicking fine (screwdriver to ear) and the dark plug end indicates a weak spark.
 

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Call me a cynic but I never get excited about thinking i know the cause of a problem until it's fixed. Renault 5 GTT ownership many years ago taught me that!
The misfire on mine was very weird...when it did misfire at idle (after months of frustrating me) you could pull the coil pack off and then at a certain distance it would start sparking and running completey ok.
Think I paid 85 quid for a s/h ig module so that should be a starter. As I said, if you can borrow one (tis a 5 min job to swap) first to confirm this is ideal.
Someone also told me that the wiring harness that runs along the cylinder head can get heat fatigued (it does get bloody hot)
 

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Discussion Starter #18
Weird thing about mines is that it doesnt miss on idle (if it does its not bery noticable)) and worsens as you put the throttle on. This forum is great for tech help as a lot of the members are very helpful.
 

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For about 2 months it ONLY did it under load at high temps..i.e impossible to trace under the bonnet when parked up. Problem was, it also had a duff coilpack which made it tricky to diagnose.
As for reference about the forum...yes...whether you are or are not a member...I have saved so much money and grief by asking a question and having someone go 'ah...yes..I know exactly what that is'

To be honest...if the internet didn't exist I would never have contemplated buying a skyline GTR
 
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