Spark Plug Change Gone Wrong?

[Nacho]

Changed spark plugs on the weekend and now she's idling really rough and blowing black smoke everywhere. Searched and dug up this old thread but didn't really help coz firing order never changed.

http://ftoaustralia.com/v3/viewtopic.ph ... plug+order

Sounds a lot like only 4 or 5 cylinders are firing. Any thoughts? I'm reluctant to go out and buy new leads.

[Bennoz]

Hey Joel, yeah certainly sounds like firing order aint right - or the wiring plugs that go into the coil packs aren't quite snapped on properly..

[Nacho]

I hope it's that simple. I've tested the resistance on the leads via multimeter and 2 leads gave me 15000 ohms and one lead 10000 ohms. Is that still ok?

I also pulled out all the new plug and replaced with the old plugs and still the same. It's kinda weird though coz all 6 of the new plugs have black tips now (carbon deposit). What could cause that?

And why all 6?

[Nacho]

I've put the leads back on and tighter than a virgin. Still running like a b*tch.

And just to confirm...coil connections are:

1-4
2-5
3-6

[Bennoz]

Ok, let me wip up a sh*t diagram

Rear Bank
135
246
Front bank

And yep, connections are 1-4, 2-5, 3-6

[Nacho]

Thanks for that Ben. So any thoughts about why I've got black tips on all the new sparkies I pulled out? The sparkies also seemed wet (with fuel) almost as if I'm not getting enough voltage to produce a spark? What annoys me more is that it was just a routine spark plug change and all I literally did was move the plenum to the side and changed the spark plugs.

Do you know how to test for damaged coil packs? How could I have damaged the coil pack by just unscrewing it and pulling it out?

[Bennoz]

Ooooh, sounds to me like the plenum (manifold) isn't sealing properly. Can you feel any air escaping (or should I say being sucked in) round the manifold seal when its running?

[I8A4RE]

Yeah thats what I would be checking first. Then make sure all plugs and vacuum lines are plugged in also.

[Nacho]

I hope this isn't a stupid question but what's a vacuum line?

Hmmmm....I think you guys are right. Hopefully gasket maker is enough.....just to confirm then, the only part I need to seal on the plenum (apart from throttle body) is the 6 ports going into the intake manifold in the centre of the V? I don't recall anything on back of the plenum.

[vipfto]

yip and vacuum lines run from black box on firewall (driver side) to manifold and also from TB

[I8A4RE]

Yep and there is also the big one that runs to the brake booster

[Nacho]

OMG I feel like such a Noob!!! But you guys were spot on....I can't believe all it was, was that tiny little hose thing I forgot to plug in at the back of the plenum!!! And this was after spending ages testing every spark plug, lead and coil pack!

[Bennoz]

Glad you got it sorted! That FTO of yours has certainly seen some good times.

[I8A4RE]