So I have a 94 F 150 5.0L. Just recently I noticed a drastic decrease in what little fuel economy that I already didn't have. Within the last 6 months I've done a almost full tune up except for the tranny. I have a intermittent chest k engine light on but no hard code. Need some expansive knowledge. I do have a expensive me hani al background but always open to advice.

 

Welcome to the site..

No memory code stored?

How is it running? Idle erratic, running rich/lean, misfire etc? If there's any guess, you could have a tailpipe reading done to see where it falls in idle/cruise standards..