Abysmal Mileage Despite New O2 Sensor

[Phaedras]

What the FRIGG. Alright, new O2 and cone filter and msd coil and NGK plugs and accel wires and two full tanks of Techron cleaner and synthetic oil and dialed the timing back to 20 degrees and STILL I have really crappy mileage ranging between 20-22. Almost NO change when I'm on the highway as opposed to around town. This SUCKS.

 

Whats wrong? I know this is an AT but I have no CEL on. So there's no reason why I should be burning so much fuel?!?

[NorthWet]

I have read that some people recommend resetting the ECU after an EGO sensor replacement... might this be relevant? Or is this just old wives tales?

[85Sub4WD]

Resetting the computer may be a good idea - and give it a few weeks to learn the new sensor

 

Actually, that is about right for an AT car - but when I did my FI conversion, I stumbled across a faulty computer that ran my car VERY rich - swapped it out with one from a '92 Loyale - 25mpg CITY (that was after 18mpg city) - but it is a MT car - but I have a very LEAD foot - a spare computer may be a good idea anyway

 

Do you accelerate hard? - that GOBBLES gas

 

and what RPM is it cruising at? - if it is overreving durring dayly driving, you may have a transmission issue - check for tranny slippage too - both will give you horrible gas mileage

[Phaedras]

Hmm, I reset the ECU TWICE, made sure I did it right. RPMwise I'm usually always between 3000-4000. I admit that I accelerate hard to make up for the EA82 SPFIs lack of horsepower, but I didnt think it would affect things THIS much. BEsides, I thought that a performance coil would help quite a bit with MPGs.