A petrol scenic 2 I drive when hot took several attempts to start the other day,then spluttered and missfired with no pull at all untill it died then was a so and so to start for 10-15 minutes. When it did finally start for several miles it missfired terably.Eventually it settled down, I have driven it for about 250 miles with several starts hot and cold without any further problems. Renault main dealer took a look at it today and found nothing wrong and as no warning measage or fault log recorded they could do no more.Now I have heard lots of stories of coil packs packing up and wondered if this could be one of these coil packs failing and would not necessarily show a fault on the vehicle log.I would be interested in any comments from any one with experiance in this area.
rust bucket (the original)
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Miserable scenario for everyone, you ,because you have a dented confidence in the car and the repairer, because it is an intermittent fault which unless manifesting itself at the time is almost impossible to diagnose.
We can either wait until it fails completely then diagnose the fault or, after checking for obvious faults and errors in wiring,notably earthing points, component connections and security and DTCs (Diagnostic Trouble Codes) on the engine management system, begin to replace the most likely suspects.
Personally I favour the first approach, wait until it stops or you can reproduce the fault to order then try and diagnose the fault.
Failing coils would not normally log a DTC unless going short circuit in the primary, low-voltage stage. Usually it is the secondary, high tension, stage which fails.A failed coil would not cause a no-start situation, just a regular misfire with resulting loss of power.
My suggestion would be coolant temperature sensor as the other likely culprit, the crankshaft position sensor will flag a DTC if it fails.
Andrew
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Simplicate and add lightness!!
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How bad is the misfiring? I assume you have two coils packs, each firing to plugs. When one of them starts to go you really do lose a lot of power as you are only firing on two cylinders. So the early stages of one dying usually gives the sensation of being in 3 gears too high for a couple of seconds. This happens more and more over time.
I wouldn't risk letting it get really bad, as letting it misfire all the time can kill your cat. I've found this out the hard way. So it might be worth just buying a new coil pack and replacing it, trouble is finding out which one is duff (maybe replace both then!). This might still be cheaper than throwing money at a garage for diagnosis. They are about £40 per pack and take all of 5 minutes to change, so a very easy DIY job (just need a small Torx bit).
Might be worth checking your spark plugs too, incase they have seen better days.
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Thanks for the help, There is a coil for each spark plug - mounted directly ontop of each plug.The missfiring was so bad that I could not pull away it just had no power.When I did get going it was if the foot brake was intermittently being applied.I understand what you are saying about the cat ect,but its a company leased car and 9 weeks old so still in warrenty.I have now clocked up 600 miles since it occured without it repeating and will probably clock up another 600 this week. I have prebooked into Renault dealer on Friday as a precaution if it missfires again.
rustbucket (the original)
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My 2000 model Megane developed similar problems which got worse until I called the RAC while on holiday. The diagnosis was one failed coil pack. Was taken to a very helpful main dealer (!) who told me that I would need all 4 coils replaced . The Sagem coils wew replaced with Denso models under warranty in about 30 minutes. Result - happiness.
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Hi, I've had a few Scenics in my time and when I lived in France I had a coil pack go at 80,000km - the guy said the cars were very reliable indeed; they all went at 80k !
About 6 weeks ago I turned 52k miles on the current version 2 Scenic and guess what - yes the first one went.
and last night, the second one went.
I got the garage to do the first one but I'd like to do this one myself - anyone know the procedure? Where can I buy the Denso or Sagem ones?
thanks
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