Technical Possible Catalytic converter issue

[fiatireland]

Hi All,

I connected the new scan tool at idle and an image is below:

oxygen sensor 1 short term fuel trim looks out of range on idle but maybe I need to drive?

Any guidance appreciated

Thank you

 

[koalar]

Can you graph the data

Pre O2 sensor should look like this

Swinging from 0.2-0.8V approximately


Not sure thats the correct fuel trims


Should be one long term and one short term


At idle LTFT and STFT together should equal 0 plus or minus 10%

What's the inlet pressure at idle

 

[fiatireland]

Thank you Koalar - I found the new tool has graphing after all!

A screen capture below - oxygen sensor 1 varies between 0.1v and peaks of 0.8v

But oxygen sensor 2 does show varing from 0.1 to 0.8v but nowhere near as many changes in the waveform. Also while the engine warms is steadily rises from 0.1 to 0.8 v over about two minutes and then starts changing between the high and low values

Inlet manifold absolute pressure starts at around 50kpa and settles around 32kpa when the engine is warmed

Any cluse from this what is going on? Sensor 1 looks like its functioning and i imagine that because the oxygen 2 voltage level changes its probably functioning? Any advice appreciated

 

[koalar]

Inlet manifold absolute pressure starts at around 50kpa and settles around 32kpa when the engine is warmed

As it should be, engine is correctly timed, the valve clearances are okay, there's no big vacuum leak

oxygen sensor 1 varies between 0.1v and peaks of 0.8v

Working correctly, the erratic scan is just a slow sample rate of the scan tool


No idea on post O2 never watched one warm up

 

[fiatireland]

Thank you - Leaving the scan tool runnning while the engine idles the oxygen sensor 2 short term fuel trim stays solidly at zero . whereas the sensor 1 varies up to about 15% - I dont think the sensor 2 should stay at zero constantly even when the sensor is varying voltage - any ideas? does it point to a catalytic fault do you think?

 

[koalar]

Short term fuel trims on there own aren't useful

We need short term fuel trims plus the long term fuel trims

Ideally together they should be around 0

Plus or minus 10% is considered normal

Under 20% is still normally Okey then it starts to become a bit grey 30% need looking at

There no such thing as second O2 fuel trims on these cars, the scan tool is confusing it with. A two bank engine like a V8