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Discussion Starter #1

I have 2008 Laguna III petrol 2.0 with M4R engine, around 60k miles on clock. Seems that it has developed a strange fault.
When ever I go for a long drive around town it sometimes starts idling very rough and struggling to pull off from traffic lights. Keeping revs above 1500 when sitting at lights help to overcome it a bit. Turning out to motorway and driving at higher speeds makes it go away. Switching off and on again makes no difference unless for over 15min or so. When power goes it stalls and then shoots forward way more than I press pedal.
No engine lights or error codes surprisingly. Drives nicely when cold.
Took it to the garage and obviously first thing they changed all 4 spark plugs and coils, although they say no fault could be found. That made the drive a bit more smoother, but after a while the same problem is back.
Took it to another garage and they honestly did not find any fault, because even though mechanic drove it around for quite a while, he could not replicate the fault. It's just way too random sometimes. Told me to wait until it gets worse and/or error codes come up and come back then.
I'm not sure at what to throw money next. Seems this engine has no EGR valve. MAF sensor? Cat? New car :)?
Would appreciate any ideas, thanks.

Premium Member
Scenic II, 2004, K4M761, DPO
4,826 Posts
Only one way to tackle this if you don't want to spend a lot of money while wasting a ton of time - Renault speaking scanner - either a mechanic you can trust with one or you buy one yourself.

Log all engine parameters while you are driving and experiencing the issue and post the log of all the values here - I am sure by looking at the data, one will be able to identify the problem area..

With only the above info I will guess a throttle pedal potentiometer problem and if correct will be very easily seen on the logs
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