Can anyone help me diagnose this?

[poohlikeshunny]

I have my #2 cyl misfiring...when I have the engine running and i pull the coil off the other 3 cylinders, the car bogs like it should...but when I pull it out of cyl 2, no change. I put my hand on top of the spark plug hole to feel for any vacuum leaks, but there don't seem to be any.

Now I DO have a ripped ignition coil boot...it's ripped almost all the way up the side...when I pull it out of the cylinder, you can see it arcing near some of the cracks/holes in the rubber, but when I pull the other coils out of their respective cylinders, I do not see any arcing at all.

Does this sound like just a bad wire? I originally had a stripped plug hole, but I tapped it and used a steel insert with the plug and now it feels pretty snug. I plan on replacing all of the plug wires just ot be sure...but could anything else be causing this misfire? Everything is smooth except for cyl 2...

Thanks in advance!

[b.u.ti-ful]

I'm not sure exactly where you are seeing arcing, but that has to be fixed.

[poohlikeshunny]

If you pull the boot out, a normal coot would have the hole in the bottom where the sparkplug fits into to be secure. Well, I have a vertical tear, and about one inch up from the the bottom (where the hole is) I see arcs of electricity coming THROUGH the rubber...which I assume is one of the holes or cracks. Here is a vid to give you a better idea...

[b.u.ti-ful]

I would say that the power is grounding through the insulation (arcing) and never makes it to the plug where it is supposed to make the arc.

[marko]

bmw wires are expensive & are 'lifetime wires'. no need to replace them all - just the busted one. my got ripped as the plug flew up & against the hood, when my thread failed while driving...

[poohlikeshunny]

Originally Posted by b.u.ti-ful

I would say that the power is grounding through the insulation (arcing) and never makes it to the plug where it is supposed to make the arc.

I'm glad someone else agrees with me. I saw arcing occurring much higher up where a solid rubber boot would normally not allow...so since the other 3 did not arc like that I am hoping the one wire is all I need.

marko, i have a full set of wires that I'll probably do anyway, but in case I have trouble in the future, can I reuse the wires that still work? And do they all have to be matched to the cylinder (ie wire 2 goes to cyl2, wire 3 goes to cyl3, etc.) I want to make sure if I only do the one that it gets done right...especially since the car fires up fine...but is only misfiring in cyl2 (or rather...not firing)...

[Xenocide]

Uh, didn't I respond and tell you it was grounding out and to replace it in another thread????

why create this one?

[poohlikeshunny]

Well I actually started the thread because I was looking for what else I should be looking at if I put the wires in and it still misfires. At this point I checked the vacuum seal in the plug hole by running the engine without the cyl 2 coil pack and putting my hand over to check for any wafts or pulsations of air...nada. My intake does not seem to be leaking anywhere...

More than anything I'm hoping the wires will do the trick, but I have a sick sensation (knowing my luck) that I will swap out the wires and it will make no difference...and i will still have a dead cylinder...

[Xenocide]

using your hand tells you nothing, the cylinder looses pressure as the motor runs over and over again. You need to do a proper compression check (which i wouldn't even do because you need to replace the wires anyways). I am willing to bet the wire is the problem.

[poohlikeshunny]

ok...so i replaced just the one wire and it fired up!! I was ecstatic (still am) to have my ride back...only thing now, is that sometimes if I let it sit and idle for a few minutes at about 700 rpms, it will dip down to about 250 and act as if it is about to stall, but then it comes right back up to 700. It's not consistent either...it kinda happens or it doesn't...does that sound like a leak?

[b.u.ti-ful]

Yeah, probably an air leak somewhere in the intake.

Similar to this thread:

http://www.318ti.org/forum/showthrea...highlight=idle

[poohlikeshunny]

good looking out! I hope it's simple...would an intake leak be the type that will intermittently cause a drop in idle like that?

[Xenocide]

yes.

[poohlikeshunny]

awesome...if a vacuum hose is relatively new and in good condition, but looks like there's a minor tear beginning where it connects, can you just use one of those steel bands that tightens it up? or would a new hose be necessary? the tear isn't big at all and the rest of the hose is ok. it looks like someone tried to force it on a little on the one end...

[Xenocide]

new hose