Hey guys. My 2001 1.8 16v astra (Z18XE) only does about 26 mpg. now i'm sure that its supposed to be more like 36 mpg? i have removed the throttle body and gave it a good clean but still no better. somebody mentioned the thermostat being faulty but i cannot see this myself? something about it affecting the cold start valve.
I have plugged in op com and done some monitoring. the fuel/air ratio is rich most of the time but every so often changes to lean for about 1 second then back to rich. NOW HERES WHERE I'M CONFUSED! O2 sensor 01 fluctuates between 50 - 840mV whereas O2 sensor 2 stays constant at 784mV. so does this mean that sensor 1 is faulty and this is why the ratio is rich, or is this how it should be? just for the record there are no fault codes being show.
I know this is a bit of a techi 1 sorry. all your feedback would be appreciated guys!