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Technical Disconnecting the Lambda Sensor

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Technical Disconnecting the Lambda Sensor

andyr

andyr

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hi all the wife has a 1242cc Mk1 1999 Punto 60SX which has been idling a bit lumpy I tried the test of unplugging the lambda sensor wire up at the bulkhead near the bonnet where the black square plastic cover is and then the engine idled lovely and smoothly then.

just a question I tried searching on here but not very successful but If i left that lambda cable disconnected would it ruin the cat on the exhaust and make the car use more fuel because as far as I can see the lambda sensor on the exhaust measures the amount of fuel going through the engine and adjusts the ECU for more or less petrol am I correct on that?

So has anyone drove around lots with it disconnected altogether without it wrecking the engine or cat converter?

If I were deciding to change the lambda sensor one day how easy do these unscrew from the exhaust? - bear in mind you are talking to a person who in the past has sheared bolts off engines before when they have been seized!! - what happens if the lambda sensor is a bugger to get out and snaps or cross threads? - does this happen often?

Cheers for any helpful advice, :)

Andy.
 
Check the cambelt timing (they jump on that model) and check plugs and leads before going too far with lambda.
Mixture too rich will eventually ruin CAT. The CAT can only control emissions which are already in limits defined by Lambda.
And yes most certainly to use more fuel.
 
The Lambada doesn't rust - it's stainless steel I think - so you'll be able to get it out easily, especially if you use some WD40 on it. Snip the wires on the old one close to the sensor, so you can get a proper 22mm ring spanner on the sensor. Don't use an open jaw or adjustable spanner if you have a ring spanner available.

The Fiat OE Lambo' (and some others) has a moulded-on plug / connector block, so it's complete. Screw the sensor in (use WD40 on the threads) then plug the connector to the matching plug on the car.

Some cheaper aftermarket items have just bare ended wires (about 6" long) that you have to splice to the original wires and connector block (of the old sensor). In this case, disconnect the block and remove the old wire (minus the sensor, which you just snipped off) and splice the new one to it off the car.

Don't trim the wires of the old sensor down too short.. Ideally the old wiring and connector, plus the new wiring and sensor should be the same length as the combined wire/connector/sensor of the Fiat OE part you just changed.. but it doesn't matter if the new one is a bit longer.

Ralf S.
 
Ralf S. said:
The Lambada doesn't rust - it's stainless steel I think - so you'll be able to get it out easily, especially if you use some WD40 on it. Snip the wires on the old one close to the sensor, so you can get a proper 22mm ring spanner on the sensor. Don't use an open jaw or adjustable spanner if you have a ring spanner available.

The Fiat OE Lambo' (and some others) has a moulded-on plug / connector block, so it's complete. Screw the sensor in (use WD40 on the threads) then plug the connector to the matching plug on the car.

Some cheaper aftermarket items have just bare ended wires (about 6" long) that you have to splice to the original wires and connector block (of the old sensor). In this case, disconnect the block and remove the old wire (minus the sensor, which you just snipped off) and splice the new one to it off the car.

Don't trim the wires of the old sensor down too short.. Ideally the old wiring and connector, plus the new wiring and sensor should be the same length as the combined wire/connector/sensor of the Fiat OE part you just changed.. but it doesn't matter if the new one is a bit longer.

Ralf S.
Click to expand...


thanks for that advice. If I put wd40 on the new ones thread would it not contaminate and ruin the new Lambda sensor?

I have been hearing bad things about the aftermarket ones being no good so I don't know whether to get an original fiat OEM one or not.

Andy.
 
reddy4bed said:
Check the cambelt timing (they jump on that model) and check plugs and leads before going too far with lambda.
Mixture too rich will eventually ruin CAT. The CAT can only control emissions which are already in limits defined by Lambda.
And yes most certainly to use more fuel.
Click to expand...

But the Idle runs perfectly with the Lambda sensor unplugged and lumpy when its plugged back in so thats why I am guessing its a Lambda fault and they do suffer quite a bit from Lambda faults on puntos according to other reports.

I've done plugs and leads so its not that and a garage checked the timing once not so long ago and thats all right.

Andy.
 
Hi mate
If all of that has already been done, then i would replace your lambda sensor. Theyre not that expensive, but i definitely wouldn't run it without it. As already said, it has a lot to do with controlling the fuelling and mixture of your engine. You could end up with the engine running very lean and melting a piston, or destroy your cat from running too rich. Its there for a reason.

Good luck,
Alan
 
Ralf S. said:
Yeas.. take it easy with the WD40 and the new Lambda.

Put a bit onto the screw thread of the hole, rather than onto the new sensor's thread .. and wipe off any excess.

It's just to help the new sensor screw into what is often a very dry and knarly thread.


Ralf S.
Click to expand...

I have some of that coper ease stuff in a tube do you reckon that would be better on the thread rather than wd40?

Andy.
 
I don't think it'll make any difference.. that exhaust will be about 200C after a minute or two so whatever you use will get burnt to a crisp. :) It's just to lube the thread while you screw the sensor in.

I think WD40 is potentially less harmful for the sensor - copper on there may interfere with the precious metal on the tip.. whereas WD is just a bit oily.. not much different to what the sensor gets covered in during normal use. Anyways, keep whatever it is off the sensor tip, just to be safe.

Ralf S.
 
a1ant said:
Hi mate
If all of that has already been done, then i would replace your lambda sensor. Theyre not that expensive, but i definitely wouldn't run it without it. As already said, it has a lot to do with controlling the fuelling and mixture of your engine. You could end up with the engine running very lean and melting a piston, or destroy your cat from running too rich. Its there for a reason.

Good luck,
Alan
Click to expand...

Thanks, i am off to check how much an original one is then from local Fiat Ireland garage then. I bet it will cost a lot all other OEM parts cost twice or more as universal stuff normally here.

Andy.
 
This problem with lumpy or erratic revving, when the engine is idling, is something that can make U fail UR MOT. The garages always say that they cannot carry out the emissions test because of this issue, ( annoying! ). How easy is it to change the lamba sensor over, and can this change cause other problems that will affect the MOT? :confused: All opinions welcome.
 
The lambda sends a signal to the ECU about the exhaust gas measurements it is receiving. If there's too much oxygen it tells the ECU to make the mixture stronger, if there's not enough it tells the ECU to make the mixture leaner.

If it's not working properly, the signals to the ECU are erratic - richer, weaker, richer.. the ECU is lurching from one extreme to another, so it affects the idle. Normal changes are very subtle and smaller.. kind of like when you tweak the steering wheel slightly while you're driving along the motorway, compared to slinging it from lock to lock.

If your lambda dies altogether, the ECU goes to default mode which is rich (lean would be dangerous to the engine - it would hole a piston, or burn a valve) and so you get very high CO and CO2 readings.

Ralf S.
 
Just for everyone's information, my Local fiat dealer, ( in Hounslow ) quoted £65 for a brand new lamba sensor, ( just the sensor they are not fitting it. ) The are also a couple of fiat specialist websites that also sell it.
i'm gonna try to fit it myself
 
Thats what I did mate

£10 for the sensor, and a 21mm spanner. Make sure the manifold is good and hot, as they can be right and tight b*ggers to move.

JUST MAKE SURE YOU DON'T RING IT !!!!!!!!!!
 
oseibonsu said:
Just for everyone's information, my Local fiat dealer, ( in Hounslow ) quoted £65 for a brand new lamba sensor, ( just the sensor they are not fitting it. ) The are also a couple of fiat specialist websites that also sell it.
i'm gonna try to fit it myself
Click to expand...

I got a price for a sensor from my Fiat dealers in Sligo Ireland. 135.00 + vat (EURO) not in stock and they would have to order. And thats not a fitted price I would have to fit it myself.

Andy.
 
Check out the www.shop4parts.co.uk/ website, as they quote approximately £67 inc VAT for the sensor, ( for a Punto Mk1 ). I'm not sure if they charge extra for delivering to ireland or not though. There may be a delay in delivery as well.
 
Just to check I'm doing the right thing, I understand thet the lamba sensor is the device i've pointed out in the picture, ( on a Punto 55S Mk1 )
lamba1.jpg

This is neat the front of the engine, ( notice the fan just above )

And the bit that connects it to the ECU is in the picture below, ( near the back of the engine )
lamba2.jpg

so I just fit the new lamba ( with its wire connection ) into these two parts of the engine. Thats right isn't it?
 
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