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Author: Subject: One black dry sooty plug
Tinks1

posted on 10/5/24 at 10:16 AM Reply With Quote
One black dry sooty plug

Hi

I have a standard 2.0L Pinto in a MK Indy and I am getting one black dry sooty spark plug always number 3, running on a weber 32/36. I have tried

Swapping plugs

Swapping leads

Distributor round 180 deg.

removed PCV valve

Had block re-bored, skimmed, new pistons and rings, head skimmed, new valve guides, unleaded inserts, new valve oil seals

only using E5 petrol

Still No. 3 black and sooty mis-firing all the time

Any help appreciated ............ getting frustrated

John

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coyoteboy

posted on 10/5/24 at 10:31 AM Reply With Quote
Stock manifold? What's your carb placement like? Sounds like uneven airflow/fuel jetting somehow.
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Tinks1

posted on 10/5/24 at 10:38 AM Reply With Quote
Hi coyoteboy

Thanks for your response

Yes stock manifold replaced existing manifold when swapped from 32/34 to 32/36 weber, thinking of putting original manifold back on. Not sure how I can alter to carb placement seems well positioned with the studs

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nick205

posted on 10/5/24 at 11:58 AM Reply With Quote
Leak in the head/manifold gasket?
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Theshed

posted on 10/5/24 at 01:25 PM Reply With Quote
Have you eliminated cylinder leakage with a compression check? I assume so.

When you say you have turned the dizzy around did this have the effect of ruling out lobe wear on the distributor? I am trying and failing to think that one through in my head.

A tappet too tight?

If those things are ruled out then maybe you are looking at fuel pooling in the manifold or some such.

What was the last thing you touched before the misfire appeared? usually a good place to start.

You have my sympathy - these things drive you mad.

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number-1

posted on 10/5/24 at 02:12 PM Reply With Quote
What plugs are you using? And have you tested that the plug/lead is firing?

Maybe look at getting plugs that can handle hotter temps and make sure they are gapped right.

The carbon or soot on the plugs are causing the misfire as it is conductive and creating a path to misfire.

Maybe a worn exhaust valve not opening up enough to let the gasses out properly? However id start with the easy stuff and check the fueling.

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adithorp

posted on 10/5/24 at 05:50 PM Reply With Quote
Constant misfire or just under load?

Why turn the dizzy 180deg'? What ignition does it have

[Edited on 10/5/24 by adithorp]





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Tinks1

posted on 14/5/24 at 07:57 AM Reply With Quote
Hi Guy's
Thanks for all your help.
Problem seems to be solved for now, checked spark plug on No.3 against block appeared to be getting a good spark put plug back and started engine still the same pulled off that plug lead no change in engine running, so swapped plug with No.1 and problem moved to No.1 but not sooting up the plug. Put in another set of new plugs seems to be running great for now ............ lets see when weather comes back

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