Lambda Query

[c7trp]

Sorry for the long post...

 

I'm chasing a poor cold staring problem and today noticed uplugging the lambda probe makes no difference to the running engine. If anything it idles a little smoother and certainly seems to start better. (My thinking being if the lambda is sending duff signals, unplugging it will set the ECU into default mode)

 

I'm using this to check the sensor.

 

At 2750 rpm I'm seeing around 850mV a lot higher than the site suggests (450mV). I'm checking this on a DVM as I don't have an O-Scope.

 

Removing the probe shows it to have a biscuit colour on one site and more black on the other side.

 

Is it shot?

 

Anyone got any experiance in testing these?

 

EU3 engine XPower 140

 

Oh, BTW - A recent RR Session showed the AFR to be very lean ...

 

Cheers

 

Edited to say, there is about 10v on the heater pins

 

Edited by - Tim Pollard on 27 Sep 2008 17:36:58

[rj]

The ECU won't run closed loop until after at least 30sec. The sensor need to warm up.

 

Once the ECU has entered closed loop the output ougth to oscilate between 0 and 0.85V - the suggested 0.45V is as stated an average. If you've always got the higher reading the ECU will assume the engine is running rich, and therefor reduce the fuel. In other words if your engine is running lean and you've got a 0.85V reading from the sensor this is probably faulty.

[c7trp]

Ah - the engine was hot - I'd just refilled, bled and tested the cooling system, so the engine had run for a good 15 mins. So assume the probe is hot - but I see that this isn't related to my starting niggle.

 

I had SWMBO bring the revs up whilst I watched the meter, from memory, it climbed from 550 mV to 850 mV.

 

Thanks for your help

 

[rj]

The probe will need to warm up each time the engine is started.

 

The engine also need to be warm before closed loop is entered. I think this happens at a water temp of approximately 70 deg,

 

It is only at the lower load sites the engine runs closed loop and also only if the throttle pot signal is stable.

 

It might be easier to check the probe at idle as you certainly will be within the limits of the closed loop.