Terrible fuel economy

[carlhako]

Hi Guys

Ive got a series 1 AU with about 284k's showing. ever since ive had it i get around 250ks or less to a tank around town. So far i have replaced the oxygen sensor that made no difference at all. not sure where to go from here. It appears to be running super rich at operating temperature it blows a little bit of black smoke but the engine does not burn any oil. Engine doesnt seem to miss has smooth acceleration altho i think its lacking power but have not driven any other au falcons to compare.

some suggestions on what to check/replace next thanks.