Faulty lambda ? - Alfa Romeo Forum
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Faulty lambda ?

Hello there,

I own a Alfa Romeo 33 1.7 ie and I am afraid I have a faulty lambda, but before I go out and spend my last money, I'd like to be more sure.
So I am looking for some advise.

  1. Uses excessive amounts of fuel (I only use the car around town)
  2. Gas pedal feels it's hesitating but picks-up at full throttle
  3. idle is rough, going up (1000) and down (600)
  4. It seems to only do this in the winter
  5. The rough idle and throttle hesitation appears for +/-15 minutes and disappears again for +/-15 minutes
  6. After resetting the ECU the rough idle disappears (for awhile)

  1. Flash-code reads 1223, "HO2S Regulator Inner Adjuster Reaches Minimum Or Maximum Value Of Correction" (<- according to some chart I have, but I am not the full 100% sure the chart is for this ECU).
  2. Checked exhaust for leaks (stuck a cloth in the back), although it has got a big hole at the beginning of the silencer, no leakage before the lambda.
  3. lambda voltage goes up to 2 volt, according to my digital multimeter.
  4. heater element measures 8 ohm.
  5. took the lambda out and looks good (if that means anything) see photos.

Thanx a lot, regards

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These symptoms may point to the failure of the lambda sensor,
but the high fuel consumption might caused by other problems as well:
- defective fuel pressure regulator, or vacuum loss at the pressure regulator control chamber
- any small vacuum leak between the throttle valve and the intake ports of the cylinder heads
- wear of the engine (camshaft wear, cylinder & piston ring wear) this can be checked by a compression test
- defective thermostat
- clogger air filter
- wear of the spark plugs / ignition leads
(or combination of above)

Irregular idle might caused by:
- small vacuum leak between the throttle valve and the intake ports of the cylinder heads
- sticky (and/or clogged) idle actuator valve

Regarding the voltage: the digital multimeters are often responding slowly to
voltage changes, at the other hand 2 volts is too much, because the sensor output voltage
shouldn't excess 1.1 volts, typically the peak voltage is around 900-950 mV.
I'm using oscilloscope to check the sensor voltage (Alfa 33 oxygen sensor signal at idle - YouTube)

There's another way by connecting an exhaust gas analyzer upstream of the catalytic
converter, while the engine is running at operating temperature, and the sensor is
connected, the CO percentange of the exhaust gas shouldn't be above 1% at idle RPM.
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