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Bad lambda sensor ?

Hello there,

I recently measured the exhaust for my 33 (1.7IE Cat+Lambda, 1990) and the mechanic told me that the lambda sensor is "bad", and needs replacement.
On the computer there, there was a number (1.234) which, he told me, was the reason for a bad sensor. He told me that the value should be around 0.9. What' this number and what is the corect value? Is the sensor really gone?
The O2 value was 1.3 %.

Please help !!! tnx
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An Oxygen sensor is a chemical generator. It is constantly making
a comparison between the Oxygen inside the exhaust manifold and air outside the engine. If this comparison shows little or no
Oxygen in the exhaust manifold, a voltage is generated. The
output of the sensor is usually between 0 and 1.1 volts. All
spark combustion engines need the proper air fuel ratio to
operate correctly. For gasoline this is 14.7 parts of air to one
part of fuel. When the engine has more fuel than needed, all
available Oxygen is consumed in the cylinder and gasses leaving
through the exhaust contain almost no Oxygen. This sends out a
voltage greater than 0.45 volts. If the engine is running lean,
all fuel is burned, and the extra Oxygen leaves the cylinder and
flows into the exhaust. In this case, the sensor voltage goes
lower than 0.45 volts. Usually the output range seen seen is
0.2 to 0.7 volts.
The sensor does not begin to generate it's full output until it
reaches about 600 degrees F. Prior to this time the sensor is
not conductive. It is as if the circuit between the sensor and
computer is not complete. The mid point is about 0.45 volts.
This is neither rich nor lean. A fully warm O2 sensor *will not
spend any time at 0.45 volts*. In many cars, the computer sends
out a bias voltage of 0.45 through the O2 sensor wire. If the
sensor is not warm, or if the circuit is not complete, the computer
picks up a steady 0.45 volts. Since the computer knows this is
an "illegal" value, it judges the sensor to not be ready. It
remains in open loop operation, and uses all sensors except the
O2 to determine fuel delivery. Any time an engine is operated
in open loop, it runs somewhat rich and makes more exhaust
emissions. This translates into lost power, poor fuel economy
and air pollution.
The O2 sensor is constantly in a state of transition between high
and low voltage. Manfucturers call this crossing of the 0.45
volt mark O2 cross counts. The higher the number of O2 cross
counts, the better the sensor and other parts of the computer
control system are working. It is important to remember that the
O2 sensor is comparing the amount of Oxygen inside and outside
the engine. If the outside of the sensor should become blocked,
or coated with oil, sound insulation, undercoating or antifreeze,
(among other things), this comparison is not possible.

So if your mehanics reading are true your Lambda is slowly dying..
So maybe you can drive it like this for few more 1000km or more ..but it will die anyway.. so start looking for a new one..
Bad Lambda sensor ussualy don't make troubles on open highway but it's real pain to drive it like that in city traffic..(from my own expirience)
BOSH serial numbers for Lambda
33 1.7 i.e. 1.7 - 77 kW 92-94 >>>0258003290
33 1.7 i.e. 1.7 - 77-79 kW 86-92 >>>0258003060
33 1.7 i.e. 16v 1.7 - 95-98 kW 90-95 >>>0TA5F-P3C1
33 1.7 i.e. 16V 1.7 - 95 kW 90-95 >>>0258003060
33 1.7 i.e. 16V Sport W. 4x4 1.7 - 95 kW 90-95 >0258003060 33 1.7 i.e. 4x4 1.7 - 77 kW 92-92 >>>>0258003290
33 1.7 i.e. 4x4 1.7 - 79 kW 90-95 0258003060
33 1.7 i.e. Sport Wagon 1.7 - 77 kW 86-92 >>>0258003060
33 1.7 i.e. Sport Wagon 4x4 1.7 - 77 kW 92->>> 0258003290
33 1.7 i.e. Sport Wagon 4x4 1.7 - 77 kW 88-89 >0258003060 33 1.7 i.e. Sport Wagon 4x4 1.7 - 79 kW 90-95 >>0258003060
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Zuty 13,

tnx very much for the reply. The problem is exactly as you said: no problem with fuel consumption on the highway, but in the city trafic....16 l/100km (6.5km with 1 liter of fuel).
Huge fuel cons. Earlier last year, fuel cons was about 11 l/100km, wich is closer to the reality. And another thing: someone told me that I can put the lambda sensor from another cars as well, that is if the sensor has 3 wires. Is this true?
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Three Wire -Colour Connection
Black - Signal
White - Heater
White - Heater

And yes you can fit the other car Lambda..
(it must be 3 wire conection like in your Alfa, and the best thing is too look at simmilar Fiat cars Regata i.e.;Tempra i.e; Tipo i.e. etc..
try to find Lambda from almost same power car like your 77kw, and be sure that the lenght of conectors is the same or longer I think Alfa 33 have 170cm lenght of wires..!!! But measure it to be sure..because it's not good idea to get shorter and then resoldering manufacturer recomends the soldering on Lambda since it will loose sensitive data due to bigger resistance on soldered place)
And stay with Bosch lambda sensors... Or use universal Universal Zirconia Sensor (Output 0.1 to 0.9 Volt)
but they will last shorter time...then Bosch original..
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