Plug leads

My 2000 RR 4.0 has a misfire on cold start due to a plug plug lead breaking down (again) The miss continues at least until normal operating temperature is reached. The LR genuine part (Leoni suppression) leads seem to need replacing every two years or so. Is it that the leads are subject to too much heat? Is there a particular one in the eight that is the favourite to fail?Are there any leads on the market which are less prone to breakdown in this way? I have a BMW E30 car which has the same leads after 18 years!

Reply to
David Haggas
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On or around Fri, 12 Sep 2008 21:39:23 +0100, "David Haggas" enlightened us thusly:

try fitting BMW leads? :-)

failing that, Magnecor are regarded as good if they cover that motor. I've had some and I reckon they're pretty good - the principle difference I noted was better quality components.

Note that the larger sizes won't fit in standard lead clips on the engine. the 8mm ones will fit in 7mm clips, apparently without harm.

Reply to
Austin Shackles

"Austin Shackles" wrote in message news: snipped-for-privacy@4ax.com...

Yep, that's about right.

That's exactly it. Heat radiated from the exhaust manifolds is what does it.

All are susceptible, but more so the 2 centre ones each side, from experience.

Not really, all leads are killed by heat eventually but the biggest issue is the use of leads with the incorrect end fitting at the plug - your engine uses thinner than previous plug bodies and "normal" leads will not seal against those plugs so the moisture gets in and corrodes the lead end fitting and plug connector.

LOL!

Magnecor do indeed make leads to fit the later "Thor" variant of the engine but I have no idea who stocks them.

Another thing to check as well as the leads - Thor engines seem to like eating their HT coils as well. Easy spot though, if you have 2 cylinders misfiring which share a common coil and the plug leads look ok, then check the coils carefully. Most decent aftermarket diagnostics systems will give you misfire detection codes and tell you from the code which cylinder is misfiring on that engine. (Common coils:- cylinders 1 & 6, 8 & 5, 4 & 7, 3 &

2) Badger.
Reply to
Badger

Thanks for the replies. I found all the connectors to be good except for one which had indeed let moisture in and corroded the lead end and plug top. I have given all a thorough clean including the plugs and ensured connections are good. This has solved the problem so thankfully the leads do not need replacing. The magnecor ones do look very well made but would the problem I've had still occur? Are the LR genuine (Leoni) ones that are fitted not made specifically for the thinner plugs? They seem to click on quite tightly. I'm surprised how just one out of the eight got so corroded.

David

Reply to
David Haggas

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