5 replies to this topic

[Steve-O 2014]

Does anyone know what could be causing this? 

 

Plug 4 won't fire unless you pull the lead off and like rest the lead on it half on. If you push the lead fully on so that the contact inside the lead "clips" onto the spark plug contact then it won't fire at all.

 

It seems it will only fire if there is a gap between the two contacts.

 

I have tried another spark plug and also another ignition cable but still the same. 

 

The dizzy cap and rotor arm look clean

 

Any suggestions? Thanks

[Steve-O 2014]

tested the lead with a multimeter and it seems fine.. Plus they are virtually brand new with only about 1000 miles on them

[Steve-O 2014]

Fired full set of new plugs in and all is well. Strange how the one in that was less than a year old and my spare plug both caused the same issue!! 

 

 

Is it right for a 998 to gap the NGK's to 0.6mm gap (Unless running electronic ignition then gap to 0.8mm?) Checked the gap on them and 3 were set to 0.9mm and one 0.85mm so set to 0.6mm

[KernowCooper]

Why that happens is when a plug goes down or is fouled by pulling off the plug lead creating a gap between plug and lead you induce a bigger voltage from the coil so it fires the duff/fouled plug, you can see this on a scope if you have a cryption. 25thou is ok for a standard ignition.

 

O.6mm is fine on the gap.

[Spider]

Another possible reaon for the misfire is the Plug Boot has become conductive, this can happen for a number of reasons, the most common being dirty next to that, depending on what quality they are, overheating.

[Steve-O 2014]

Thanks. Im running No Ballast ignition / coil with an Aldon Yellow is the 0.6mm gap still ok? When I switch to an electronic ignition should I set to 0.8mm? 

 

If the boot was conductive then surely I would have been getting a big shock when taking them off while the engine was running?