2002 Bora 2.0L
177k kms

- Very bad fuel economy.
- Took into mechanic. Car had not been scanned for years.

These errors came up:

16518 bi-si no activity
16500 coolant temp plausibility
17536 long term fuel trim multi bank 1 system too lean
16555 bi fuel system too lean
17990 idle adaption at limit
17978 engine control unit blocked
16684 missfire detected
16688 cyl 4 missfire detected

Apparently after the codes were cleared, none came back after a test drive.

However, I have noticed no improvement in the fuel economy.

I finally bothered to fill up the whole tank. I first noticed the fuel indicator only went 3/4 of the way!
Anyways, the car chewed up petrol like anything, it hits empty, I'm thinking ive only driven 350ish kms the indicator is prob dodgy, but when I filled up I was able to put in 53litres which is pretty much a whole tank.

So I got 350km (a lot of highway kms) from a full tank!

Any ideas guys?

I havnt had the fuel filter changed the couple years that I have had it. MAF?
I really dont trust any mechanics here in Canberra.