saxo furio 2002 - Lambda sensor problem or not?

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Sun 7 Nov 2010 09:28
saxo furio 2002 - Lambda sensor problem or not? - winnerkev

I have the unenviable task of sorting my daughters car out for her to sell .

Please can someone tell me the least expensive way of diagnosing whether i have a fault with sensor 1 sensor 2 or the cat itself. The ecu light has been on and diagnosed vaguely by the garage as the emmisions but these have been tested separately to be ok. i can do the work myself i think as i have already removed the post cat sensor thinking i might sleeve it it as mentioned elsewhere but am not sure if that will work or even if its legal. How can you tell if a sensor is faulty?Cheers any one.

Kev

Reply | Report as offensive | Link
Sun 7 Nov 2010 11:37
saxo furio 2002 - Lambda sensor problem or not? - elekie&a/c doctor

Idealy you need the use of a diagnostic tool that will read live data from the engine control system to assess the operation of the lambda sensors.However if the emmisions system have tested ok,then I would assume the lambdas are working ok.Perhaps it is showing a cat efficiency fault.This is enough to put the mil light on but not affect mot emmision limits.hth

Reply | Report as offensive | Link
Sun 7 Nov 2010 12:51
saxo furio 2002 - Lambda sensor problem or not? - injection doc
saxo's are prone to air leaks from vacum pipes triggering off lambda sensors faults. If you have a volt meter you could take a reading from the pre-cat sensor and rule of thumb when hot it should be switching 4 times a second and should respond instantly if you blip the throttle. If the car has a fuel problem you may find the voltage readings will be constant at one end of the spectrum. You would normally expect the sensor to switch between .2&.8 of a volt.
The post cat sensor if the pre cat sensor and cat are working should be constant at .55 of a volt. If the cat isn't working the voltage will vary like the front one.
The 2nd sensor monitors the cat effiency and sometimes aftermarket cats are known to trigger of the 2nd sensor.
To check if the cat is working it needs to be very hot and the car held at 3000 rpm and take an infared temp senosr reading on the neck of the cat in and a 2nd reading on the neck of the cat out, if you have a 50 degree difference the cat is working, if the temps are more or less the same the cat is failing.
Reply | Report as offensive | Link
Sun 7 Nov 2010 15:49
saxo furio 2002 - Lambda sensor problem or not? - winnerkev

you may be on to something

i have done a diagnostics and it came up with the following.

P0420

Catalyst system efficiency below threshhold Bank 1

pending DTC during current or last completed driving cycle.

Oxygen sensor data Bank 1 sensor 1 0.440v sensor 2 0.450v

short term fuel trim 0.78% rich +

Any idea what my options are.

Kev

Reply | Report as offensive | Link
Sun 7 Nov 2010 19:27
saxo furio 2002 - Lambda sensor problem or not? - injection doc
check long term fuel trim, but fuel trim should alway be within a max of 20%
what it means is that its over compensating for another fault. i would check for air leaks and a map sensor eading at idle. check fuel pressure etc.
0420 is a cat efficency issue but can be cause by a mixture issue. check the vacum pipes to the air box, I trust this car hasn't been fitted with a K&N ? these cause havoc , even just the oil impregnation can cause issues
Reply | Report as offensive | Link
Mon 8 Nov 2010 11:47
saxo furio 2002 - Lambda sensor problem or not? - winnerkev

Thanks everyone plent for me to chew over there. kev

Reply | Report as offensive | Link