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Discussion Starter #1
Car runs fine when cool or warming up.
When car warms up (oil and water both up to temps) the car develops a stumble / miss on a cylinder (or so it feels like its only one cylinder)

It idles rough and hesitates when accelerating while missing as the revs climb...BUT ONLY WHEN WARM /HOT.


What is causing this? Maybe when the coils get hot they are weak? Anyone run into this?
 

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Discussion Starter #3
Im buying a set of NGK iridiums BCPR6EIX monday morning and testing the coils for resisitance also. Hopefully something becomes obvious when i pull the coils.

i really hope that is the issue. I have to be in top condition by tuesday for a dyno run.
 

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Discussion Starter #4
I Swapped coils as i had 3 physically damaged and 3 test bad. The car has DENSO Iridium plugs with unknown mileage so tomorrow i am pulling them for a set of NGK Iridiums. Also ordering new Splitfire Coils tomorrow.

So once i have new coils and plugs.... What could be the problem if it STILL does this...
 

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is it not lambda sensor when it gets hot? goes into closed loop mode or something, wait untill it hapens again and disconect the plugs by the right hand suspension strut.
 

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Discussion Starter #6
I swapped out the Denso Iridiums for NGK Iridiums.... HUGE difference much smoother. Much crisper. BUT when it heats up it stutters a little. ALOT less than before though, must be the coils now. Splitfires just ordered, hopefully here before friday.

Ill update then.
 

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Hey Donk I Had splitfires and iridium 8's put under mine and it fixed a major misfire prob at 5000rpm and above when on WOT.

I am however getting a slight rough idle when water/oil up to temp like yourself and I'm pretty sure its the o2sensor giving up or seeing better days as I had similar trouble on older cars. Try replacing that first - its a shedload cheaper that the £400 british notes I coughed up for splitfire coilpacks.
you could try www.justlambdas.co.uk or nengun may sell em?

the other cheap alternative (but temporary mind!) is if your taking your coilpacks up, try wrapping a good strong insulation/elec. tape around the cylindrical bits a few times - this is said to eliminate any rough idling or misfire trouble but dont think it'll last forever. If it fixes it then you know its your coilpacks going :)
 

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Discussion Starter #8
Thanks very much for the info. I think ill replace it also...

I just paid the equivilent of 260 GBP for a set of Splitfire Coils from Japan yesterday morning...

We will see how it goes when the coils show up. But i should prob replace the O2 anyways just for maintenance sake.
 

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yeah the o2 sensor is worth doing - its next on my list after the cambelt - I can handle a little rough idling - just not a snapped belt!!
260quid - bloody hell thats good pricing - I paid 380 :( well worth it and they'll look cool under the hood too - bright blue - you may not bother having the coilpack plastic cover over the top haha! In fact why on earth is mine covering them up?!!?!
I found the delivery is really smooth with them tho - slight flat spots and hesitations all the way up to 5krpm on mine then the big misfire above that - the splitfires sorted all this out and it howls all the way to redline happily now. You'll not be dissapointed donk :D
 

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Discussion Starter #10 (Edited)
Just an update...

Replaced the coils with Splitfires and it really cleaned the engine up as far as running alot smoother.

Still have a slight stumble... its like someone is using a switch.. i can sit there and idle fine.. then it starts to miss... then its fine again... does this at every rpm. And if you turn off the car. then restart it... the miss goes away

Its not an idle issue as this happens through out the RPM range. Im sure its something stupid like a sensor somewhere...
 

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Discussion Starter #11
So... NO ONE here has a basic understanding of the Skyline Ignition system?!

It cant be the 02 or it would be a constant issue not just when the engine is hot... not warm... but up to tempurature and running around town

So could it be faulty MAFS?
Worn out igniter?
Crank Sensor?
 

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Discussion Starter #12
I pulled the codes tonight out of frustration (should have done this first) and got a code 21.

This leads me to believe the "transistor pack" ignitor pack ontop of the coil cover is on its way out. Am i correct in assuming this?
 

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argh. my car is doing this too - only when hot, and only during the day, oddly enough. Runs perfectly in the cool night air :p
 

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where is the O2 sensor located? I figure I oughta take a look at mine as well.
 

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o2 sensor located in the downpipe off the turbo. got a plug in it mate and the thing looks like a sparkplug located in your downpipe.

donk - sounds like the next step - if the plugs n coils are good then working backward would suggest that the amplifier at the back where the plugs feed from is faulty - try doin a swap with a friend and seeing how it goes :)

(I am of course assuming this bit is replaceable - I've never had mine off haha! new coilpacks sorted misfiring issues for me straight away)
 

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ok, I know exactly where it is, and I'm betting the farm that my O2 sensor is overheating - because there's a leak in the pipe just before it that's making things very hot there!!
 

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Discussion Starter #17
yes it was the amplifier (little silver heat sink looking thing on rear of coil cover) I swapped with a friend and she runs mint now.. ordered a new one from Adam @ FEAST in Japan. Good price. You know its good if i say it is! lol!
 

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I found a 1-2mm gap between my turbo and the exhaust manifold! Bolted it all back up, sealed it, so far so good.
 
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