Renault megane scenic 1.4 16v misfire
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By billlincs - Thursday, January 19, 2006 4:42:50 PM
hi all

i have a megane scenic 1.4 16valve in, sorry i don't have the engine code at the minute. problem is a misfire throughout the rev range. i thought it would be a coil gone, as with the engine running,(badly) if you unplug coils on number 1 and 4 plugs, the engine dies, but unplug no. 2 or 3 and it makes almost no difference. swapped coils( 1-2&3-4) and fitted new plugs, still the same. compression fine on all cylinders. anyone had the same? no codes, except coil circuit, caused by me disconnecting them!

do the injectors cause any problems on these.

please help,


By ovy1255 - Thursday, January 19, 2006 4:45:53 PM
wen u say injectors is it multi point or 4 seperate
By ovy1255 - Thursday, January 19, 2006 4:48:00 PM
are 2-3 plugs firering [feeds to coil 2-3]
By billlincs - Thursday, January 19, 2006 4:50:57 PM
thanks ovy,

didn't get chance to check feeds, thought it was bound to be the coils, as we've had loads of those go. is there a seperate signal for cyls 1&4 and cyls 2&3?


By Speedy - Thursday, January 19, 2006 4:51:18 PM
Had this a while back with a 1.6 megane ..................

Turned out to be a faulty coil Wink

By manicmotors - Thursday, January 19, 2006 4:51:33 PM

what year is it?


By billlincs - Thursday, January 19, 2006 4:52:32 PM
Sorry martin, it's a 2001


By Dave Hill - Thursday, January 19, 2006 5:00:36 PM
These modern coils are weired when they fail

I have noticed on Focus's mainly that when the coil packs fail on a cylinder, when you pull the offending cylinder HT lead off, that they actually run better, as opposed to not making any difference. Whats that all about?


By DaveH - Thursday, January 19, 2006 5:03:54 PM
Pull off each injector plug in turn to indentify which cylinder then replace that coil pack !!!!


By ovy1255 - Thursday, January 19, 2006 5:07:39 PM
i wud check if 2-3 plugs are wet

check all for spark

double check compresion [h/gasket between cylinders]

feeds to coils

but like u i have changed loads of these and always in 2s

By billlincs - Thursday, January 19, 2006 5:14:30 PM
thanks daves,

i swapped the 2 firing outer coils, with the inner two, and it made no difference, so i'll check feeds and injectors tomorrow.

first job is the old austin 6 though... 1 carb, 1 coil, suck squeeze bang blow! wish i were born around 1930!


By manicmotors - Thursday, January 19, 2006 5:27:00 PM

i have a feeling there is a problem with earths on these i will check in the morning at work


By DaveH - Thursday, January 19, 2006 5:32:54 PM

I did all that and it was still one coil....Smile

See if you can get hold of a test one and swap them one at a time !


By K And R - Thursday, January 19, 2006 5:33:58 PM

Do as Dave says pull the injector plug as this gives a better clue than the pulling the plug to coil. One other thing if it one coil  has gone fit all four as they are getting updated all the time, and if one has gone the others won,t be far behind.


By Mike H - Monday, January 23, 2006 2:25:14 PM
The coils on renault are wired in pairs, if I'n not mistaken 1&4 and 2&3 in series, thats why its easier to pull of the injector plugs to identify which cylinder is misfiring.

As for cahnging all 4 coils, check the make. If its Sagem change all 4....
Denso and JCAE are much better quality.Cool
By gary - Monday, January 23, 2006 3:08:57 PM
By billlincs - Wednesday, February 08, 2006 5:14:55 PM
Hello again,
Very sorry but i thought i'd already posted on curing this one, i changed the coils on cyls 2&3 and everything was fine.....
Until yesterday when it came back with exactly the same problem! Pulling leads from coils 2&3 makes it run better! pulling coil 1 or 4 stalls it, and pulling injectors 2 or 3 makes no difference.
it's been only three weeks and around 1500 miles since i "fixed" it, so what could be causing it to fail so soon? I spoke to renault and they have no problem replacing the two coils under warranty, but will the next two fail so quickly too?
i fitted new NGKSad plugs at the same time as the coils, could this be a problem?
Compresion test ok, sagem coils, from Renault,( where do you get the others?? Denso etc?)
Any help much appreciated.
By Dave Hill - Wednesday, February 08, 2006 5:38:16 PM

Just a thought I know unlikely, but it should be ruled out. I have had problems with inlet fanymould gaskets giving me the run-around on these engines. Also head gasket failure in between cylinders two & three??? They can give unexpected compression test results.



By K And R - Wednesday, February 08, 2006 5:58:40 PM

Dave could be right,BigGrin it will be a firstBigGrinBigGrinBigGrinBigGrin. sorry dave, please don,t send Paula to kick meBigGrinBigGrin. but there should be numbers on the coils to know if they are the latest. If your dealer won,t confirm yours are the latest please PM me the numbers and i will check them or just post them and i suspect some-one will beat me to itBigGrinBigGrinBigGrin.


By billlincs - Wednesday, February 08, 2006 6:07:33 PM
Thnks dave, but why should fitting new coils cure it for a few weeks if it's an air leak or head gasket prob?
Kev... i'll post and pm the numbers tomorrow when i get to work
By Dave Hill - Wednesday, February 08, 2006 6:27:26 PM

I agree totally mate, but surely you have been in the game long enough to know that sometimes there seems to be little logic involved in these types of faults.

I posted a while back about a Scenic 1.6, 8 valve that we did a head gasket replacement for a local Vauxhall dealer. We had a good few hours afterwards chasing a misfire that was there one minute & wasn't the next. That turned out to be the inlet manifold gasket. I was amazed how random it was.

I am still learning (The hard way sometimes) to check the things that you would normally rule out before moving onto more costly areas.



By billlincs - Friday, February 10, 2006 7:05:41 AM
I think you've jinxed me Dave.
Changed all coils and plugs (again)., still the same Sad.
Checked all round for air leaks, compression tested and... Cylinder 3 down about 25%,( cyl 2 ok!), although it was ok when the car came in the first time! maybe it already had a slight leak and the plugs/coils change made it unnoticeable?
I'll whip the top off after lunch and will let you know what i find.
By maxmell - Friday, February 10, 2006 7:28:29 AM

Dont want to muddy the already murky waters but we had a clio

in with the same engine last week,similiar fault turned out to be 2


By DaveH - Friday, February 10, 2006 8:48:43 AM
BigGrinWinkBigGrinWinkBigGrinWinkBigGrinWinkBigGrinWinkBigGrin   Don't ask !!


By billlincs - Friday, February 10, 2006 6:10:20 PM
how did you trace it to the injectors neil?
i think i'm gonna change jobs.....
all getting tooo heavy
thinkin of becoming a binman!
By maxmell - Saturday, February 11, 2006 3:55:17 AM

Last resort!was an intermittant slight miss usualley under load tried coils etc,luckily i was able swap the injectors and rail from another car.

Although they were working i think they were slightly blocked.

Binman sounds good pay/pension/working hours/stress etc etcBigGrin

(forgot customers and finish at dinnertime)

By Dave Hill - Saturday, February 11, 2006 2:19:04 PM

You forgot to mention that they only work one day a week.    w00tw00t