Zach

Cylinder #2 not firing.

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Confirmed #2 by unplugging coil with no change to idle or running.

No fault codes.

New coils, new plugs.

 

Worth knowing that for about 20 seconds the car dropped another cylinder but returned to firing on 3 again. This has not happened again.

No smoke at all and engine still sounds mechanically mint, no knock not even a tick. just the rough 3 cylinder sound and the smell of petrol.

 

Spark plug comes out black and returns to silver with the rub of a cloth which makes me think it must be seeing some sort of ignition like a very weak spark from hidden electrical problem or extinguished by huge amount of over fuelling.

 

With no codes its pretty hard to figure out.  At this point Im thinking a damaged tooth on the sprocket.

 

Any ideas?

v7sti bug eye

 

update: Under boost car runs alot better with the coil plugged in than without, but does not feel smooth, micro jerks felt. I'm thinking that the injector might be fire hydranting into the cylinder and making it null on idle but giving a weak combustion under boost. No smoke, sometimes 1 or 2 bangs when taking off in first gear from cold start.  I'm gona try replace the injector unless anyone thinks otherwise?

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Did you get new leads as well? if you havent tried swapping the leads I'd try that too, the wifes car had a dodgy boot and was arcing, dropping the cylinder every so often.

If you still have the old plugs check any for signs of arcing along the porcelain section. 

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Sorry I should mention that Car is v7 sti. no ignition leads, coil on plug.

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7 minutes ago, Zach said:

Sorry I should mention that Car is v7 sti. no ignition leads, coil on plug.

Still check the end of the boot, my wifes car uses coil on plug, there was a small hair line crack in the inner part of the bottom plug/boot. Also with a slightly leaking valve cover leak made it worse as the oil would travel up the crack and make the misfire worse. Get a torch and have a look at it and see if you can spot any cracking, might need to pull another as a reference.

Once I swapped it out with a new one the car ran sweet.

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Coils are new, boot inspected when installing, shes solid. Thanks for input though.

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Sorry, totally forgot reading that you had new ones, Im getting old and my memory is not so good these days, when it never was great.

Hopefully someone else has a better answer

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1 minute ago, SpeedySub said:

Im getting old and my memory is not so good these days, when it never was great.

 

Your fine lol looks like a pretty human mistake to me friend.

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Rather than replace the injector get it flow tested with the other 3 that will tell you if it's working properly or not.

 

Is the wiring to the coil getting a solid 12v with ign on? Wiggle the plug/wiring on it see if the voltage changes might be as simple as a dicky connection. The coil should have 12v and each time it's fired it is grounded by the ecu. If it doesn't have 12v then you most likely have bad wiring or something. 

 

Move coil to different cylinder and see if the problem remains on the cyl 2 or moves with the coil. If it remains it's probably wiring or ecu related, or worse case something wrong with compression etc. And if it moves with cylinder then replace that coil and see if you just got a dud coil.

 

 

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Late reply I know, but I'd definitely check the wiring, if the problem stays with cyl 3, even with new coils then I'd strip the loom back a bit from the plug and check it all. 
They're bad for breaking right at the plug from heat and just getting too weak with the heat cycling.

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