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Discussion Starter #1
Hi guys,

Is the lambda sensor (by the Cat) on a clio 2 supposed to report a constant voltage?

Background info:

Clio 1.2 Grande, 2001 Y reg.

I've just had my cio in the garage following the engine missfiring badly and losing power. After searching these forums I changed my coil pack, leads and plugs with no change. Eventually found the fault to be a blown head gasket between 2 and 3 (2nd time this has happened to me :() I had this repaired but there is still a slight missfire at all revs and at idle. Garage cannot find anymore faults and recomend replacing lambda sensors.
Also sometimes when I start the engine a big plume of smoke will come out the exhaust.
 
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Depends if it's a heated one or not. If it is, then yes as it has a heating element in it to pre heat it. Should have 2 signal wires, then if it's heated, a 12v pos and an earth.
 

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Engines of this vintage will use 'narrowband' or 'switching' zirconia lambda sensors. The sensor output is around 0.1V when running lean, and rises to about 0.9V when running rich. There is a rapid transition from one voltage to the other at close to the ideal 'stoichiometric' fuelling condition.

On later OBD-II engines, two lambda sensors are employed. One, before the catalyst ('regulating'), will be kept constantly switching either side of stoichiometric as the engine ECU controls the fuelling by varying the fuel injector opening time.

The other, post-cat (or 'diagnostic') sensor operates pretty much at the stoichiometric condition - so the sensor output is fairly constant at about 0.6V.

The sensors only work when hot, and all modern systems employ heated lambda sensors to reduce the time taken for the closed-loop system to 'come on-line'. Also, the sensor outputs are ignored under acceleration conditions.

Your sensors will be 4-wire jobbies. Two are for the heating element, and will both be isolated from the sensor body. The other two will be the sensor element connections - one is the 'live' output, the other being the earth (ground) return, which is either also connected to the sensor case, or (more usually) isolated from it.
 

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Discussion Starter #5
Thanks, so its normal for the lambda to run at a constant voltage.

Not sure where to look next for the source of my problems...
 

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Thanks, so its normal for the lambda to run at a constant voltage.

Not sure where to look next for the source of my problems...
Can you tell if the smoke is bluish (oil), blackish (overfuelling) or whitish (steam)?

Sorry madnoel - you answered whilst I was typing!
 

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Hmm - you might still have a slow coolant weep into one or more cylinders, which is then 'burnt off' at start-up.
 

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Discussion Starter #10
I've had the head skimmed, the gasket replaced and then rechecked once my misfire started again. The garage assures me its not the gasket again. The engine isn't overheating.

I'm gonna try putting my old coil pack back on tonight just incase I've bought a faulty new one since that wasn't the problem in the first place.

Does anyone think my problem sounds like a lambda fault?
 

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Discussion Starter #13
High guys, found my misfire fault. It was a lead shorting on the engine right down by the sparks :forehead:.

I've changed the lead and the misfire is a lot less noticible, kinda wondering now if its the spark thats shorting.

My sparks are Bocsh.
 
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