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Michael Toet
TryHard
Vic
V8

Posts: 245
Reg: 06-2009

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Saturday, January 15, 2011 - 08:58 pm, by:  Michael Toet (Myke31) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Help please...

I got all the plugs out, and plugs 3, 4, 5 & 6 were black. 1, 2, 7 & 8 were good.

The only thing I can see that is common with 3, 4, 5 & 6, is they are the longest leads. They are all driven by the dizzy/coil pack that sits in front of the opposite bank. Could a bad earth reduce spark to these plugs due to the longer lead?

I also found the firing order is 1, 8, 4, 3, 6, 5, 7, 2. The bad plugs all fire right after one another 4, 3, 6, 5. No idea if that means anything or if it is just a coincidence.

What else do they have in common? Does anyone know what can cause these centre 4 cylinders to have black plugs?

Thanks,
Mike
Jol Alexander
DieHard
Vic
UZZ31 V8 (no mods)

Posts: 754
Reg: 07-2009

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Monday, January 17, 2011 - 02:05 pm, by:  Jol Alexander (Courage) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Do they all sit on the right dizzy?...
Michael Toet
TryHard
Vic
V8

Posts: 246
Reg: 06-2009

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Monday, January 17, 2011 - 02:13 pm, by:  Michael Toet (Myke31) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Nope, Jol. On each bank of cylinders the middle two are clagged. These are driven off the dizzy located on the opposite bank. So the two on the left are off the right dizzy, and the two on the right are off the left dizzy. However the remaining two cylinders driven off either dizzy are all good. So not consistent, and I was left wondering why only two out of 4 on each dizzy are black, and why is it only the middle two cylinders?

Thats why I figured it probably wasn't the dizzy or the coil packs (all of which are new).
Daniel Arndt
TryHard
Vic
UZZ31 LTD

Posts: 212
Reg: 03-2010

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Monday, January 17, 2011 - 02:43 pm, by:  Daniel Arndt (Darndt) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Must be the ECU then Mike. Either it is the problem or is causing the problem. Meaning if the caps or drivers are bad in the ECU it could be over fueling these cylinders. OR the ECU could be fine and is purposely over fueling these cylinders. EG faulty sensor telling the ecu it needs more fuel.


Your replacement ECU shouldn't be too far away anyway.
I'd also do the O2 sensors just for the hell of it. Ive read somewhere you can get universal ones which work fine.

Let us know how it goes.
Tom Richards
DieHard
nsw
V8

Posts: 525
Reg: 08-2005

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Monday, January 17, 2011 - 05:20 pm, by:  Tom Richards (Tomr) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

have you measured the resistance of the leads?

if you do a search, resistance has been posted previously. looking outside the square, if they are low quality leads, they could all be "failing" to some degree, but the effect will be more noticeable on the long ones
Michael Toet
TryHard
Vic
V8

Posts: 247
Reg: 06-2009

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Tuesday, January 18, 2011 - 11:22 am, by:  Michael Toet (Myke31) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

No, I haven't measured the leads. They are NGK, and the plugs are NGK platinum.

I pulled the plugs out again after a short trip and they were nice and grey. The trip would not have allowed the engine to heat up to operational temp (plus ECU would have still been in open mode - Or is it closed?). I am wondering if heat is an issue.

Dan, still waiting on the ECU. Hopefully I get it today.
Andy Losurdo
Tinkerer
NSW
v8 quad cam

Posts: 95
Reg: 02-2007

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Sunday, March 20, 2011 - 08:14 pm, by:  Andy Losurdo (Funny_guy77syd) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

i was wondering if this probelm might have somthin gto do with the injectors not being cleaned
Michael Toet
TryHard
Vic
V8

Posts: 266
Reg: 06-2009

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Monday, March 21, 2011 - 08:23 am, by:  Michael Toet (Myke31) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

It had crossed my mind, but why just the centre 4 cylinders?

I have put in a new ECU and so far the car is running fine. I need to find some time to pull out the plugs and re-inspect them to make sure.

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