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Happy - But Very puzzled

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Got the axle back together (still need to do brakes and Oils) etc

So, I thought I'd tackle the mysterious misfire.

It happened straight after a HUGE Misfire when it was cold over fueeling and "Kicked Back", splitting the plenum to AFM Hose wide open :(

Anyway............. started it .............ran it out on the drive.

Fuel Pressure - OK

Air Leaks - NONE OK (Hose Replaced)

and then worked my way through a load of things - No difference.


Replaced the original Ign system with rotor arm cap and V8 Leads - er NO

So, its not the EDIS MegaJolt then B)

WTF is it

I checked the entire system with the diagnostic manual, changed AFM Resistor pack, Checked Therootle Pot, gap on buterfly, fuel level ( :rolleyes: ok)


Sat an thought and pondered.

In desperation I changed the NGK BP7RES (1 month new) for the old ones

Ran sweet as a nut :D:D:D:D:blink:

So, happy but puzzled.

Why can / would a misfire destroy a new plug ?? :huh:


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Cheers Ralph

Went had a look (that link should be IMHO in the tech archive !) and found this


The spark plug's worst enemy! (Besides fouling)

Can break insulators or break off ground electrodes

Pre-ignition most often leads to detonation

Plug tip temperatures can spike to over 3000°F during the combustion process (in a racing engine)

Most frequently caused by hot spots in the combustion chamber.

Hot spots will allow the air/fuel mixture to pre-ignite. As the piston is being forced upward by mechanical action of the connecting rod, the pre-ignited explosion will try to force the piston downward. If the piston can't go up (because of the force of the premature explosion) and it can't go down (because of the upward mo-tion of the connecting rod), the piston will rattle from side to side. The resulting shock wave causes an audible pinging sound. This is detonation.

Most of the damage than an engine sustains when "detonating" is from excessive heat

The spark plug is damaged by both the elevated temperatures and the accompanying shock wave, or concussion


Nige :lol:

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Oh yeah Tell me about it :blink:

I had a "Fiddle" ( :o ) a while back, basically played with the plug leads on the MegaJolted V8 whilst it was on tickover, done this loads of times when it was on the original plugs and ign system - just pull a plug lead off and "Brace" yerself for the small jolt etc, to check for a misfire,.

Did this on the MegaJolted V8 a while back, the 1st plug lead I pulled off gave me a "Belt" strong enough to make me go and sit on me stool in the workshop for 10 mins, didn't even switch the engine off I felt so bad, mate did it for me (between hysterics :lol: - GIT)

Me hand up to me wrist was 101% numb .....and I felt like I was going to 'Bark' big timey :huh:

Have greater respect for the syetem since :D:lol::)


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I learnt at an early age that when presented with a broken plug, broken in a way thay exposes three wonderfuly shiney and interresting looking brass heads of the resp pins, that the careful arrangement of your fingers to enable you to simultaneously make contact with all three at the same time is not recommended either. Very exciting but not in the way I'd anticpiated :D

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My Dad introduced me to magnetos when I was about 5.

"here you go son, just hold onto this wire whilst I wind this little armature!"

Needless to say, I have passed this lesson on over the years - I have a nice ickel Ducelier Magneto from a petrol Fergie stashed away for those special times

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one evening a couple of years ago an annebriated Kombi van driver ran into a power pole outside my house. I rushed outside to find the driver slumped unconcious over the steering wheel ,obscuring the ignition key, and foot jambed hard on the throttle. There was petrol everywhere, the engine was screaming at full revs and the only thing I could think of was to open the engine hatch and reef the distributor cap off. Well in the couple of seconds it took to do that I must have received a few hundred high voltage belts that still makes me wince when I think about it.

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