Lean mixture when warm

[pezzler]

I've had an AFR guage fitted to my car for about 10 months; the gauge has always given me a consistant reading, and it has always cycled between 14.6-15.2 on idle

 

All of a sudden, out of the blue, the car has started to run lean. I seem to be getting around 12.8 from a cold start, but once the coolant gets a little heat in it and the IACV closes a bit, i'm getting 17.0 upwards.

 

I checked the fault codes last week and it threw up a code 14; open or short in AIT circuit.

 

Would a faulty AIT sensor tweak the fuelling to that extent?

 

I was thinking that the it seemed more likely to be a coolant temperature sensor fault, can anyone shed any light on this? Anyone had anything similar?

 

 

Cheers

[Tricky-Ricky]

For most sensor problem's the ECU generally runs things on the rich side for safety, i presume you mean IAT sensor? and no if this or the coolant temp sensor was duff it would be showing rich AFRs, i would be inclined to be checking the wide-band sensor or its calibration.

[pezzler]

I had an inkling that it should run rich when a sensor fails, but i'll take that as confirmation

 

As for the wideband; in the early hours of this morning I read a thread started by Steve, who had a similar problem that eventually turned out to be wideband. Not sure on the best way to test it, but i'll have a trawl about for some more info. Bit pis*ed that it may be that the wideband sensor has failed already, I could have forgiven a 17 year old OEM one

 

Thanks for your input

[Tricky-Ricky]

They can be a little fragile under certain conditions, what make of WB is it. AEM or Innovate?

[pezzler]

Its an AEM. Really havent done a great deal of miles on it, kind of expected more from a recognised branded bit of kit

 

On the plus side, I guess the sensor is only about £60 ish so mustnt grumble