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Ask Mike Kelly Your Own Question
Mike Kelly
Mike Kelly, Auto Service Technician
Category: Renault
Satisfied Customers: 5470
Experience:  17 years experience as an auto mechanic, foreign and domestic. 5 years running my own repair business.
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The mil was on on my Renault Megane 1.9dci 120. A fault code

Customer Question

The mil was on on my Renault Megane 1.9dci 120. A fault code was stored relating to the egr valve. I cleaned the valve, which was very dirty and cleaned a lot of soot from the intake manifold. A couple of days after doing this the mil went out and stayed out for about a week. It then came back on intermittently and eventually stayed on all the time.

Scrolling through the "Test Mode" menu on the car's computer, this stated a fault with the coolant temperature sensor and maf. I disconnected the battery, replaced the coolant temperature sensor and egr valve with new items and cleaned the maf with electrical contact cleaner.

Immediately after doing this it was like a different car. It started slightly more quickly (I never felt it was slow), idled more smoothly, pulled more strongly at all revs (in particular low revs where previously it would need almost 2000rpm to pull strongly it would acceleration well from around 1300). It also revved to 4500 much more like a petrol engine whereas previously there was no point really revving it above 3000. Response to pressing the pedal was more immediate too. Curiously the mil was not extinguished.

I then didn't drive it all week as my wife drives the car most often. Next time I drove it, it seemed like it was before I replaced the egr, cleaned maf, etc. i.e. all these improvements have gone. Both the maf and coolant temperature sensor faults on the "Test Mode" screen on the computer have gone. Mil is still on.

It has always used no oil, fuel economy is good, no excessive smoke, no untoward noises.

What do you feel the issue could be. Do you think that the maf is faulty?
Submitted: 3 years ago.
Category: Renault
Expert:  Mike Kelly replied 3 years ago.
Hi,my name is mike and I will assist you with your question.
From what you have described and replaced,the issue is consistent with the mass air flow sensor being faulty. When you cleaned the sensor the issue was corrected,however I believe the sensor is electrically failing and resulting in these symptoms. Replacing the mass air flow should solve this.