Renault Megane - Renault Megane rough running

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Wed 17 Aug 2022 14:16
Renault Megane - Renault Megane rough running - Dave N

Renault Megane, 2001, petrol, 1.6 K4M engine. Came out of the shops and it was running rough, On the way home lack of power, funny smells, and engine light flashing periodically. I've had the usual coil problems before, so removed connectors one at a time with no difference, apart from the engine nearly dying with each connector removal.

Any pointer to potential areas?

I may buy a cheapy code reader to try, although I read somewhere that a flashing engine light doesn't set a code, only a permanent on light.

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Wed 17 Aug 2022 15:12
Renault Megane - Renault Megane rough running - elekie&a/c doctor
Very likely to be a coil problem . These fire in 2 pairs , so if one coil fails it knocks out another.
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Wed 17 Aug 2022 21:08
Renault Megane - Renault Megane rough running - Dave N
How do I test for this? I unplugged one at a time, and each time the engine nearly dies, suggesting that no one coil was bad. It’s had bad coils in the past, and the pull one at a time test showed the duff on.
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Wed 17 Aug 2022 21:27
Renault Megane - Renault Megane rough running - elekie&a/c doctor
Leave all coils connected. Remove the 10 mm bolts from each coil . Start the engine and carefully lift each coil one at a time and see what happens.
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Thu 18 Aug 2022 20:57
Renault Megane - Renault Megane rough running - Big John

This really sounds like a coil pack issue - sometimes testing at tickover doesn't show up the offending one as it only really shows up under load. I had this with my previous Octavia a couple of times in the 19 years our family owned it. The funny smell could be unburnt petrol hitting the hot catalytic converter. The first time it had this issue I drove about 8 miles in fault condition and even though fault sorted it struggled on the next MOT re emissions requiring a new catalytic converter.

As it failed a couple of times I took to carrying a spare coil pack - replacement took 5 minutes!

Edited by Big John on 18/08/2022 at 20:59

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Fri 19 Aug 2022 06:58
Renault Megane - Renault Megane rough running - Dave N
Thanks for the help. Haven’t looked at it yet, but might just get a set of coils anyway. It had quite a few coils in it’s early days, but none in the last 10 years or so. I don’t know if they improved the quality, or I just got lucky. Was only thinking the other day I haven’t need coils for ages!
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Mon 5 Sep 2022 19:31
Renault Megane - Renault Megane rough running - Dave N
Update: I bought a set of 4 Valeo chineseum coil packs, and so far, so good. Haven’t run it up the road yet, but it started and idled as it should. So thanks for the help and suggestions.
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Mon 5 Sep 2022 21:33
Renault Megane - Renault Megane rough running - Big John
Update: I bought a set of 4 Valeo chineseum coil packs, and so far, so good. Haven’t run it up the road yet, but it started and idled as it should. So thanks for the help and suggestions.

Since posting I've remembered something about this model of car - I think there is a plastic bolted down pipe assembly (thermostat?) that can fail and spray water out under stress straight onto a coil pack or two? Depends on the precise model probably but I remember sorting one out for a colleague - needed a couple of coil packs as well. Does the coolant ever drop - just checking just in case it'll takes out your shiny new coil packs!!

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Tue 6 Sep 2022 05:29
Renault Megane - Renault Megane rough running - Dave N
No, no coolant used. Despite the french reputation, it’s required very little over the 20 years it’s been in the family. Apart from coils, it’s had a wheel bearing, a wheel cylinder, a crank sensor with wiring upgrade, and an ABS tone ring. It had one cambelt change 15 years ago, and that’s it!
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Tue 6 Sep 2022 08:10
Renault Megane - Renault Megane rough running - Xileno

Not much wrong with MK1 Meganes, the MK2s were a different story although mine wasn't too bad overall.

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Tue 6 Sep 2022 09:30
Renault Megane - Renault Megane rough running - elekie&a/c doctor
Yes , the mk1 Megane was a generally ok functional car with only a few issues. The mk2 soon changed all that and brought back unreliable French electrical systems . I quite like the mk1 cabriolet megane . Pretty looking motor .
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