18 miles to the gallon !!!!

[carmur]

hi there

i have a bmw518i 1990 j plate.
I recently had a snapped timing belt which resulted in valves needing renewed. however over the last 2 wks or so it is eating fuel usually 18 miles to the gallon.
I spoke to my local bmw garage who said it could be the injectors.
Anyone hae any idea what could cause it to burn fuel and any tips on detecting the cause

thanks in advance

carmur

[kaoru-tochiro]

Has it had a complete tune up? Also maybe one of the sensors was not plugged in when the repairs were finished.