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post #223 of (permalink) Old 3rd March 2012
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Re: Renault Clio 2003 - Engines - Loss of power and Warning Light

Hi everyone, this is my first post - as I found this thread so useful I wanted to share my experience. My car is a nearly 10-years old Clio Authentique, so with the 1.2 8-valve engine, and it has done over 100,000 miles, mostly trouble-free (apart from worn-out mechanical bits like brake discs, clutch, wheel bearings etc.).

My first incident was typical of those reported: I was about 1.5 miles from the house, on my way to work (a road closure had forced me to deviate my usual route), coming off a roundabout, sudden loss of power, 'electronic fault' warning light comes on. I pull out of the traffic as soon as I can - once stopped, the revs are wildly fluctuating, from perhaps 1,000 to 3,000 rpm. Engine off, grab handbook to see what the warning light means - ponder options for a while, then decide to have a go at re-starting engine, and to my surprise it seems to be fine again, so I drove straight back home.

Extensive Googling found this thread and other similar ones on other forums, and since it was clear there were wide variety of potential causes, I decided to wait and see what would happen before taking any other remedial action. I only had to wait for about a week, when the same thing happened, only this time I was about a mile further away from my house (this time on my usual route). Same deal, loss of power with no warning, and the dreaded 'electronic fault' light on, wildly fluctuating revs. Since re-starting the engine worked last time, this was the first thing I tried, and again, it immediately burst into life and I was able to continue to work.

I then decided I would get my local Renault dealer to read out the fault log from the ECU , but by now I was highly sceptical that it would yield any useful information (and in this I believe I was right -see below), especially since there are literally dozens of stories of people spending hundreds of pounds unnecessarily replacing X, Y and Z in their engines through poorly diagnosed faults, often from the ECU read-out. Unfortunately there is apparently no time-stamp on the entries in the ECU fault log, so no ability to determine if what it says actually ties in with the problem experienced. Anyhow, the print out the garage gave me read:

DF002 Throttle potentiometer circuit 1.DEF

Further Googling revealed the '1.DEF' meant 'Track 1' (as opposed to 'Track 2'), but this made little sense when related to the problem, as I failed to see why the ECU should decide that whatever had happened one second warranted shutting the engine down into limp-home mode, but then a few seconds later, on re-starting, it decides everything is fine and lets the engine run?! I was also wondering whether there was a temperature-related element to my fault, as on both occasions it had happened at such a similar distance from my house.

These thoughts were cemented when the third occurrence happened about a week later, literally about 100 yards further down the road from the site of the second incident. This time however re-starting the engine did not clear the fault, so limp-home back to the house I actually did! I had already decided that the first place to look would be the throttle body , on and on removing the inlet manifold feeding it, the problem was clear - I have always had lots of creamy, emulsified oil on the oil -filler cap, and the inlet manifold was full it - see first photo.

The second photo shows the breather pipe coming off the top of the camshaft cover into the manifold, which is how all the sticky goo was getting in there, and this was completely blocked (the pipe feeds in at the bottom of the back of the first picture).

The throttle body itself was also badly affected - the third photo is the 'outlet' side - that little nipple at 5 o'clock I believe is a temperature sensor, and was enveloped in the stuff. (The 'inlet' side was also covered in the stuff too.)

How any of this relates to the ECU -reported 'throttle potentiometer' problem is anybody's guess!

The sticky consistency of the stuff might explain the apparent 'temperature related' component of the fault - as the engine warms up, it might start moving around more, and hence have the effect of blocking that pipe, affecting sensors/whathaveyou. Once it was cleaned off with carb cleaner, the engine runs a treat again, and I haven't had a repeat episode in over 6 weeks now. The engine isn't quite running at 100% though - there is a slight misfire at low revs - but since I was planning on changing the car this year anyway, I figure any saving in fuel will be wiped out with the cost of having it fixed. In any case I have seen an improvement in mpg - I had to fill-up the day after the third incident, and I recorded just 43mpg (and this included a long run of over 100 miles as well as my normal commuting); the next tankful after the clean-up gave me 45mpg (all regular commuting); the tankful after that, which again included a 100-mile trip, gave me 47mpg! Whilst it may not be running 100%, I'm happy that I have cured the original problem, and also that any further improvement in fuel consumption is likely to be very slight!

So, there we have it, take it for what it is - 'YMMV' as they say!

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