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Discussion Starter · #1 ·
Hi, this is the first time I've asked for advice on this forum, so I don't know the finer points of etiquette here, so go easy on me, ok?

Right. I have recently bought a 2003 Mk2 Clio 1.2 16v, to replace my long term Mk2 Megane which is sadly no longer with us.

I needed a car asap so I grabbed this as it appeared to be a good runner, and it mostly is.
However, I have found an issue when the engine is started from cold.. but not every time.
It fires up, idles ok, I drive off just fine, and then, after about 1/2 mile, it sort of misfires and loses power. If I then rev it, it coughs, Kangaroos a bit and then settles down and behaves itself.
I've had it back to the car dealer and it's been to two local garages, but each time it's been fine. Typical.
I've also reset the warning light by erasing the error codes 3 times. Hasn't happened for a couple of weeks, but the error was "fuel trim, bank 1".
I am thinking either lambda sensor or maybe coil pack, but should I be looking at simpler stuff like spark plugs?
It's only done 42k miles, and the last 1k was me in the last month.

Any suggestions gratefully received.

Thanks in advance.
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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7,237 Posts
Half a mile's worth of effortless driving after the first start sounds to me O2 related - about the time you need for the ECU to go into closed loop mode.

Since you seem to have a working scanner:

What is the value of the LTFT parameter before you start the engine cold?

Can you post a graph of the upstream O2 voltage parameter (O2 B1 S1) for a minute beginning before you even start the engine and without you touching the throttle
 

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Discussion Starter · #3 ·
Half a mile's worth of effortless driving after the first start sounds to me O2 related - about the time you need for the ECU to go into closed loop mode.

Since you seem to have a working scanner:

What is the value of the LTFT parameter before you start the engine cold?

Can you post a graph of the upstream O2 voltage parameter (O2 B1 S1) for a minute beginning before you even start the engine and without you touching the throttle
Unfortunately, it's a VERY basic scanner. No graphs. I can't see anything called LTFT in the "data stream" results..
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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7,237 Posts
LTFT = long term fuel trim.

Even a basic scanner on an EOBD vehicle should be reporting a value for that by law - can you check again?
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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7,237 Posts
OK - the reader actually is producing long-term fuel trim values - its got a problem with screen real-estate so not using all of the letters ..............
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That is actually quite a huge number at 14% ................... should be very close to 0 if all is well.

So you took these readings all after the engine ran for quite a while? - I see the engine is reporting 66C and the intake air temp is sitting at 48c ............... correct?
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The O2 sensor voltages indicate that the heaters on the O2 sensors are still ok.


If you leave the scanner on the vehicle when cold and you drive off, how long does the O2 sensor voltages take to start oscillating and what is the minimum and maximum values you see at the time you experience the "kangatoo" behavior?



So with such a huge positive LTFT compensation value, one would question why and sort that as a first step because you will most likely not pass MOT tests ..................... when the engine is cold I would not be surprised at your reported experience at all

Check for vacuum leaks in and around the intake manifold and exhaust leaks before the first O2 on the system ................... could be blocked injectors........... could be bad O2

Just my method of faultfinding - others may differ in approach and suggest something else
 
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