"I don't think my lean burn works right but I don't want to pony up for a new O2 sensor. Are you sure there isn't much of a difference between HX and CX/VX transmissions? I think HX, DX, LX are all the same gearing"
1996 - 2001 HX final drive is 3.722. 1992 - 1995 CX/VX final drive is 3.25. My '95 DX hatchback has a final drive of 4.058. If I get a 6% FE improvement by swapping in a CX/VX tranny (per the other member who did the same CX for DX tranny swap), then you are not likely to get much more than 2 - 3 % improvement.
Someone recently posted on another thread about a rough running problem w/ bad FE and it turned out to be the O2 sensor. If I were you, I'd pony up the $$ for the O2 sensor. Based on the FE in my wife's HX (w/o the mods you've done to your HX, nor the efficient driving techniques), it's highly likely that the bad O2 sensor is the source of your poor FE. And I wouldn't waste my $$ or time w/ a VX engine swap either. Trust me, the HX is an efficient machine. You just need to correct what's wrong.
Yeah, but the engine doesn't run rough at all and I've checked the o2 sensor using the guidelines from Haynes. It checks out fine, but occasionally (every 5-8000 miles) I'll get a check engine light on and it is always the primary O2 sensor.
I'll take your advice about trying to get the HX lean burning running right. I guess I just need to check the O2, like some have done here, while I am driving.