got a set of 071's in a stg 1 cossie. it recently started running on 3, so pulling off the leads one by one i could diagnose that no.1 was the culprit.

took the plug out and had a look, but not much to see. took all plugs out and cleaned them and checked and set gaps at 0.6mm (std coil), but put the plug from no.1 back into no.4. then it runs on 3 still, but this time no.4 is the culprit (so can't be the leads or HT system or anything else apart from plug)

now the strange thing (well to me anyway). when pulling the lead off the plug and putting it back on, i noticed that if the lead is properly plugged on it misfires, but if the lead is just rested on top of the plug, it fires properly

any ideas? obviously i'm going to replace the plug anyway, but i'd like to know why this happens

 

maybe the top of the plug is fooked and the only way it will make a proper contact (arc?) onto the top of the plug is if you now rest it on top of the plug? i presume the top is screwed on properly?

 

yes, the top is screwed on properly

everything looks ok on it, it must be an internal problem

 

i have a similar thing every now and then from cold, it runs on 3, you pull the plug leads off and there is one plug that as u pull its lead off makes the car run on 4, once warm though, it is fine and there are no misfires all teh way though the revs, could just be one of teh slight downsides to teh cheap plugs.

 

weird innit?

i closed the gap up a bit, and it runs fine with the lead plugged on properly now.

but i would still like to understand it.

 

yep, once its cleared the mis, it done ever do it again until its beed stood for a few days say... and some days it doesnt do it at all? might try closing them up a lil bit as mine are at 0.9 mm

 

its possibly cracked down the side of the porcelian

 

surely that would manifest itself more prominently when hot under heavy load than on cold start...?

 

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