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Discussion Starter · #1 ·
Hi all, what is the best thing to do with the lambda sensor after the cat is removed? Do I disconnect it somehow or should I just leave it as it is? :confused:
 

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Remove the Lambda sensor and the car will begin to consume more fuel! I believe in the absence or fault in the Lambda sensor, the ECU substitutes this variable with a constant. The air-fuel mixture will generally be rich.

I have removed the cat in my 155 1.8 TS 16v and replaced it with a Perry's straight flow (because I generally do not like the drone over a long drive)but the sensor is left where it is. I notice that the sensor is before the cat and not after.

This should help and if you do remove the sensor, please do not throw it away! Give it to someone, like me!

Kenneth :cool:
 
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Discussion Starter · #3 ·
Hi Kenneth
For arguments sake, is it something you know or are you guessing? On my previous car, Alfa 33 1,5 IE, I removed cat and lambda when new and drove it for over 6 years and nearly 150k km / 95k miles with no ill effects at all. I was a bit sceptical before this was done – but it works all right and it became a bit quicker though the rev range.
A auto engineer told me that the lambda basically does two things; masseur’s temperature and oxygen content in the exhaust gasses and adjust air – fuel mixture accordingly. The cat only works above aprox. 400 degree Celsius fuel mixture is not adjusted for the cat until that temp is reached and after that the mixture is enriched in order to make the cat clean the exhaust gasses (for which it needs an extra amount of unburned petrol). As the engine’s normal running temp is reached before the cat reaches 400 degrees the ECU should be able to optimise the mixture for non-cat running.
Well, the 33 run an earlier version of the Borch ECU so can work in a different way. The engineer told me that a current is send to the lambda which works as a resistance; below around 400 degrees no current is returned to the ECU – above a current between 0,1 and 1,5 volts is returned according to temp and oxygen content.
When refitting the cat and lambda (before an official road worthiness test) the car needed about 200 km for the ECU memory to adjust, but afterwards went all right and was tested to be within exhaust limits.
It could be interesting to hear from someone with experience on this with a 155.
Alfisti regards
Erik
:confused:
 

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Actually I drew my comments from experience and from another post about 6 months ago regarding the Lambda sensor.

My Lambda sensor failed after I used petrol from a station that was recently flooded. My guess is presence of water in the fuel and other contaminants. A few days after that, I noticed that my petrol consumption was higher.

After a few full tanks, I measured that I was losing 100km per full tank of fuel. That is a lot! A check with the local Alfa dealer confirmed the Lambda sensor failure. Changed a new sensor and I got back my normal consumption (550km per full tank).

The Lambda probe is esentially a transducer and the ECU 'sees' the status by means of voltage conversions. Remove it and the ECU loses this sense and has to substitute it with a constant.

Kenneth
 
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Discussion Starter · #5 ·
What happens if I just remove the 7.5A fuse for the lambda sensor. What would happen? Is the effect equivalent to removing the sensor itself? :confused:
 

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The fuse feeds the heater element within the probe. If you remove it, the probe will take a lot longer to reach operating temperature (and will cool under idle). Simplest way to take it out of circuit is find the 2 pin AMP connector and just unplug it.

Wouldn't advocate it though. Cat or not, the probe is essential.
 
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