Civic VX getting crappy gas mileage

[calchip]

I've got a '92 Civic VX (2nd one I've owned!) that I bought used about 3 years ago.

Before that, I owned a '92 VX that I bought new, and that one consistently got between 45 and 55mpg. Unfortunately, it got totally crunched in an auto accident with 185K miles and was unrepairable.

The problem is that my current VX has never gotten anywhere near the 40-50 mpg that the first one got.

Here's what I've done so far

- Car had a tune-up right before I got it (now 20,000 miles ago) I was told it probably didn't need another one.
- O2 sensor was bad when I bought it, so I replaced it. It's a 5 wire sensor.
- Cylinder head had a bent valve, so got that replaced

Just recently, the idle air control valve has crapped out and apparently didn't respond to cleaning (engine fluctuates between stalling out, normal idling, and idling at 2500 rpm) but I haven't replaced it yet.

Engine has about 100K miles on it, near as I can tell the car was well cared before before I got it, but low mileage (82,000 miles on a 12 year old car) so perhaps it sat around a lot. Given the 5 wire sensor and (I seem to remember) results of a Carfax check when I bought it, I believe the car is not originally a California car, though that's where I now live.

Any ideas? I doubt the IACV alone is the problem, since gas mileage has been crappy but stable (27-33 mpg) since I bought the car 3 years ago.