Dear All,

My 1990 Chevy G20 is running very rich (to the point of suffocation within 1
mile radius!!)

The engine is a 5.7L V8 TBI and I keep getting error code 44 (which
according to my Haynes manual means "lean exhaust" measured by the Oxygen
sensor mounted in the exhaust manifold. Clearly, it's not running lean and
my first thought would be a faulty O2 sensor as I think the ECU is running
the engine with a rich mixture to overcompensate. However, before I replace
it, does anyone have any ideas (apart from a faulty ECU) what might cause
this to happen? Is there a way I can test whether the O2 sensor is operating
properly and sending back the right information?

(I'm in the UK so sourcing parts is not as easy or cheap as in the USA!!
I'd rather investigate and order the right bit first time!!)

Cheers

Chris