O2 sensor check

[Paul Whyte]

Hi folks,

I have replaced my O2 sensors, however I want to check that they are working as seems the car srunning a little rich. Ca someone please give me simple instructions on how to test that they are working please?

Many thanks,

Paul

[extanker]

do you have a scan tool ?

[Paul Whyte]

Yes i do,
However I am guessing the figures i receive are from the ECU and not directly from the O2 sensor.

I have included a photo of the results.

I only have 2 O2 sensors on my model, precat sensors, later models had an additional 2 after the cat.

Cheers,

Paul.

[extanker]

if your scan tool has a "02 cross counts" look for a changing number ,this means its going above and below .450 mv. ....or you can monitor the 02 data while you give the motor a small vac. leak. with the system hot and idling in closed loop .450 mv is what its trying to maintain...so expect the numbers to move around [depends on the tools sample rate] ...a lab scope is better but DONT EVEN DREAM ABOUT BACK PROBING THE 02 WIRES. quickly press and release the gas pedal and look for high mv,next if you can safely go WOT for a few seconds look for .900/950 mv while on the highway at say 5000 rpm upward. OR if the check engine light isnt on dont do anything ....they are working

[Paul Whyte]

Thanks for the info, much appreciated.

I shall try testing it over 5k rpm as you suggested.

My car seems to idle a little fast at times, especially when i come to a stop (say at traffic lights) after a high rpm run.

It is also running a little rich apparantly which is causing the high emission levels during my recent test,

I was told this may be the sensors, however I am not receiving any error codes. I had holes in the exhaust but these are fixed. The high-ish reving ad idle seems to be a little worse since these have been repaired, Any other ideas? I have checked airfilter and shall replace the sparkplugs soon through matter of course, I assumed the O2 sensors may be to blame, as fuel economy seems a little low, averaging around 32 miles/gallon. Is this normal?

The car is running fine though, starts fine and is causing me no real problems except a slightly high idle, generally 1k rpm, sometimes it revs up to 1.5rpm and then drops again. It makes the car infront think I am getting impatient

Any ideas would be gratefully received.

Many thanks.
Paul.

[extanker]

check your throttle body and idle air controll valve for coking [crud]. if it failed a smog test i would think it will force a CEL . an exhaust leak can fool the 02 sensors making them think the car is lean so they richen the mix. look at injector on time [mil/sec] ....you will need normal specs to compare