02 sensor live data capture advice

[Andy03]

Morning all

I could do with some help interpreting what a live data chart of my o2 sensor is showing me. My 172 is running a little rougher than I would like and I want to rule out a failing o2 sensor. I checked the o2 sensor using torque and a line chart to record. I have included a screen shot of the chart being generated. Can anyone tell me if this is normal operation or somethings not quite right?

Many thanks

 

[da rok]

That should be a fairly constant cycle, as you can see there are a few times when it fails to cycle fully and stops short, this may point towards your rough idle, how do the fuel trims look? also have a look at your map sensor graph at idle... ive had a few dirty map sensors give trouble over the years, vacuum leaks from the carbon canister and its associated piping can also cause trouble, any vacuum leak really, that that you should see from the map sensor reading

 

[Andy03]

Hi mate. Yes I noticed the points where it wasn't cycling as it should. I'll go and record the fuel trims this evening and map sensor this evening. I did have a quick look at the pipes leading off to the carbon canister this morning I think I may need to look have a look at the carbon canister more closely

 

[Andy03]

Hi again mate here's the other graphs from the other sensors you suggested

 

[da rok]

fuel trims seem a bit high, normally they range from +20 to -20, those are the max stops unless theres something wierd going on, your map pressure is also varying more than it should... if you have any start pilot stuff spray it around the joins in the vacuum hoses and see if the revs bounce or change at all... that would indicate if there is a vacuum leak and where... also theres no harm in pulling the map sensor out and giving it a clean, as well as every other earth and connector in the engine bay... often makes quite a big difference for me... the signal wires carry so little current that the slightest bit of corrosion on the plug can cause problems

 

[Andy03]

Thanks for the advice mate. I reckon I need to have a good hunt for the leak