Civic VX cant get over 41ish MPG
 

I bought and tuned up a 92 VX with 233xxx miles on it. I put brand new tires on it which are the correct size at 40 PSI. brand new o2 sensor, the correct spark plugs/wires, cap and rotor, all new seals, factory intake with new filter, new brakes...yadda yadda yadda. I am a honda guy and i am very familiar with theses cars but I cant seam to get past the 40ish MPG range.

I drive this car 60 miles one way, mostly highway to work everyday. Ive put 3200 miles on it all averaging 41 MPG.

How can I get this this to do better? am I missing something? It does go into lean burn mode, I can feel it but I have no instrumentation to watch

We need more information.

How fast do you drive? How many times do you use your brakes in a single commute? What sort of terrain? How many miles / gallons since you finished fixing it? Manual or automatic transmission? Average temperatures?

I live in central to western PA so its all smooth pavement but rolling hills. I drive between 55-65 and coast in neutral as much as physically possible. accelerate smoothly using ~75% throttle until i reach 55-60 MPH. Its a 5 speed manual car with d15z1 lean burn vtec e motor. I have driven 3200 miles with about 82 gallons used according to my fuelly account. I rarely use the brakes and use the look a head method as much as possible minus the necessary stop lights.

You should be getting much better mileage than that. I suggest checking compression, preferably with a leakdown tester. If you are losing compression, the leakdown tester tells exactly where it is leaking. Also check the cam timing.

Have checked for brakes dragging or excessive rolling friction? Nothing should be hot after a highway run followed by light braking to a stop.

Ultragauge / Scangauge is your friend.

the car is OBD1, scanguage and ultraguage will not work.

brakes are perfect and brand new, no dragging. I also just did the timing belt and water pump so I know for a fact the mechanical timing is correct but i have not put a timing light on it yet to verify distributor timing

Advanced timing, warm air intake, kill-switch, vacuum gauge, grill block, belly pan, rear wheel skirts, interior mirrors, the list goes on...

There are a lot of options out there to getting higher mpg. What are you willing to do? Do you have a long term mpg goal?

Well I know this little vx is plenty capable in stock form to get at least 50 mpg especially the way I drive it. I still am hesitant to spend any money on instramentatoin until I can prove this car worthy to keep considering I have a crx that averages 38 mpg as is. I bought this car not knowing it was a lemon until I had already was forced to sink $1000 into just to get it into a position that I could possibly drive it or sell it if I had to. I have to be missing something if I can't get into the 50's. I am leaning towards leaking or clogged injectors or I just totally suck at driving in lean burn mode. Any advise for staying in lean burn? I know the hx civics had some tricks dealing with higher rpms around 2000 or 2500 or something. I just don't know the tricks of this vx yet I guess. It runs great though otherwise. Very healthy and reliable. I drive it 120 miles per day and recently drove it on a 750 mile round trip without issue. I just can't get more than my current best 44 mpg

Don't feel bad I'm in same boat but haven't sank much into it yet. Hooked up multimeter to watch lean burn hopefully this tank is better. You'll be amazed 4th on freeway seems to sometimes be better. I have rolling hills though. All you have to do is let of throttle and very gently apply and seems as if I'm then in leanburn. Good luck.

What speeds and rpm are you running in 4th on the highway? At 55 in 5th I'm at roughly 1900 rpm. I know vx's had two different transmissions geared slightly differently

Does that engine have a distributor? That kind of MPG would be consistent with timing retarded 5 or more degrees. Especially look at the vacuum advance. If the vacuum advance is messed up, the engine will develop full power, but get lousy MPG at part throttle.