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Spark Plugs


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Kit was misfiring only from the nearside exhaust on deceleration (release of the accelerator or when braking).

Advice a little advice at Stoneleigh, I decided to change all 6 plugs:

 

IMG_8727_zpsy7hu4wt4.jpg

 

IMG_8730_zpszsneaidr.jpg

 

As you notice from the picture above all the old sparkies looked OK, a little scorched from overheating and a nice clean sparking end, except one.

On the picture above please notice the middle sparky is covered in oil, could this be the culprit?

Considering it was on the same bank of plugs as the exhaust manifold that misfires.

 

Since changing the sparks and driving the car, it seems better but still misfiring slightly (just less frequent and more when the engine gets hotter).

Any idea why one is oily and can this be causing the issue?

 

 

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from the picture, although the thread looks oily, the electrode looks dry (but sooty). A misfire can tend to give a sooty plug, so it might be a symptom rather than the cause. Not sure if i can see any signs of overheating...?

 

What are your spark plug gaps? what is recommended?

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from the picture, although the thread looks oily, the electrode looks dry (but sooty). A misfire can tend to give a sooty plug, so it might be a symptom rather than the cause. Not sure if i can see any signs of overheating...?

 

What are your spark plug gaps? what is recommended?

 

As per workshop manual:

 

General Specifications

 

Firing Order 1,4,2,5,3,6

Spark Plug Gap mm (in) 1.3-1.45 (0.051-0.057)

Spark Plug Type XW4E-12405

Silicone Dielectric Compound D7AZ-19A331-A (Spark Plug Connector) ESE-M1C171-A

High Temperature Nickel Anti-Seize Lubricant F6AZ-9L494-AA (Spark Plug Thread) ESE-M12A4-A

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Dino. Is it back firing or popping on deceleration? I had popping on deceleration due to air leak in exhaust system. I have a black soot make on side panel that gave it away.

 

Might be worth checking?

 

Back firing on deceleration & only from near side exhaust.

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Guest lotusPaul

Backfiring from the oiled up plug on off throttle? Thatll be the unburned fuel. Swap plugs for a new set mate. Then retry. Super 4s are good, use them on the lotus and would recommend any day. I think you can also fit same or simillar iridium tip plugs that zetec use too, pricey but may help.

Cause tho is what were after, my guess would be valve seals first, may need the cover off mate. Are you down on the oil at all?

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Backfiring from the oiled up plug on off throttle? Thatll be the unburned fuel. Swap plugs for a new set mate. Then retry. Super 4s are good, use them on the lotus and would recommend any day. I think you can also fit same or simillar iridium tip plugs that zetec use too, pricey but may help.

Cause tho is what were after, my guess would be , may need the cover off mate. Are you down on the oil at all?

 

Plugs swapped and still getting same affect.

Oil fine, but will re-check again tonight.

valve seals first - unsure what you mean here - cylinder head valve seals...???

 

Was wondering if any of it could be an air leak somewhere, even thou I cannot hear it over the twin exhausts.

Any tips on a quick and easy way for checking any air leaks?

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Something you said on the brakes thread about it running fine for the first ten minutes of the journey but then miss-firing as it got hot. You have sort of proved it's not the plug and I don't think it sounds electrical. Seems to be one cylinder that is fouling it's plug. This suggests the problem is local to that cylinder. Valve stem seals is a possible or rings to promote oiling in that cylinder, worse as the engine heats up and the oil thins and 'leaks' more easily but could be fueling with a poor injector in that cylinder. If that injector was leaky and overfueling you would not notice when cold but would as ecu enrichment drops off as the engine warms up. Simple and easyish check is to swap all the left bank injectors over to the right bank and vice versa and see if the problem moves.

If you are on batch injection rather than sequential you can make a further check by swapping the injector wiring pairs left to right to prove their wiring.

 

Nigel

 

I'd do both (and compression testing) before stripping down the heads

Edited by Longboarder
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Something you said on the brakes thread about it running fine for the first ten minutes of the journey but then miss-firing as it got hot. You have sort of proved it's not the plug and I don't think it sounds electrical. Seems to be one cylinder that is fouling it's plug. This suggests the problem is local to that cylinder. Valve stem seals is a possible or rings to promote oiling in that cylinder, worse as the engine heats up and the oil thins and 'leaks' more easily but could be fueling with a poor injector in that cylinder. If that injector was leaky and overfueling you would not notice when cold but would as ecu enrichment drops off as the engine warms up. Simple and easyish check is to swap all the left bank injectors over to the right bank and vice versa and see if the problem moves.

If you are on batch injection rather than sequential you can make a further check by swapping the injector wiring pairs left to right to prove their wiring.

 

Nigel

 

I'd do both (and compression testing) before stripping down the heads

 

 

Cheers dude, I will give it a shot and provide feedback when I get chance.

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