I have a problem with Renault Megan Most likely its something with the coil but its really weird.

When i turn on the car its fine i drive for about 20-40km and the car starts to lose power like a coil would malfunction but then after 20-40km more its back to normal I want to fix it but I don't know which coil is malfunction because some times it works and other does not.

I want to avoid paying the mechanic just to plug in his computer and check which coil is broken, also i think it won't show any errors.

I could fix it myself if the coil wast working all the time i would just change one coil and drive and see it its the one that cause this but i cant because its sometimes working sometimes not. The engine light doesn't light either when the problem is active.

Is there any way to check if a coil is broken/malfunctioned without the use of a computer?



  • If a coil was malfunctioning and causing a misfire, the ECU would pick it up. The only time I've seen a coil have an intermittent problem was due to heat, but it would run at start, then when heat soaked would start running bad and not recover until the heat went away. I think your problem may lay somewhere else besides a coil. You should not fixate on them as your issue, be open minded and see what else it might be. Sep 8, 2017 at 10:33
  • Hmmm, i should also state that sometimes if i go to fifth gear on about 50-60km/h It starts goin bad too. THats just sometimes tho Sep 8, 2017 at 10:43
  • If the light's not coming on, you're going to need someone that can datalog and has experience with drivability to do a diagnosis. Throwing parts at a problem will generally be more expensive than paying someone to look at it.
    – Ben
    Sep 8, 2017 at 12:37
  • Grant gotta go to my local mechanic see whats up ill keep this question updated for anyone instrested Sep 8, 2017 at 12:57
  • If you're experiencing intermittent misfires then a bad coil isn't the only smoking gun. There is little sense in throwing parts at this problem without further narrowing down the scope of the problem.
    – Zaid
    Sep 8, 2017 at 15:48

1 Answer 1


My problem was That I am missing engine cover in my Renault (I bought it without it) the mechanic said that somehow water drops down onto the coils, He blow out the water from coils and now its grant but probably it will happen again as i live in Ireland and its raining nearly everyday :), So i will need to get a cover for my engine. The Coil itself was rusty but it was fine.

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