HI, I just got myself a used vx and been getting about 29mpg on the first tank.
I will try change the following item to improve the mpg
new o2 sensor
new fuel filter
get fuel injector clean
maybe it is our ca model, mpg not as good compare to 49 states model
I'd add a new distributor and rotor to your list. You will not find a better fuel injector cleaning and flow testing service for $18 each than www.witchhunter.com . The CA vx will benefit from a conversion to the Federal version.
I just bought a 1992 VX California emissions car with A/C and 214,000 miles on it. One owner, totally stock. He maintained at Honda on schedule. He also tracked his mpg on a msExcel spreadsheet. His range was ~34-41mpg. He told me he rarely used 5th gear because it did not feel right to him except on long trips.
The CA ecu was pulled for a Fed ecu, the '92 California VX has the 5-wire o2 sensor in place but not the ECU to make lean burn possible.
This VX is getting 44mpg in some mixed driving including steep hills in my neighborhood. That should have been more than offset by my 60mph steady highway driving. My expectation was that this car would easily hit the high 40's mpg as I have been very light on the throttle and under 2500 rpm the majority of the time.
I've got a transmission ISB that is shot and will be replaced with clutch next week. I'll post back if this changes anything.
You guys with CA emissions should pursue an ecu swap, especially if you've got the 5-wire sitting in the engine bay like mine.
How is the service at witchhunter? Do you see a big difference on the mpg after the service?
Extrodinary service, one business day turn around. I've used them twice. Every part that can be replaced is replaced and the injectors are engraved with a number and returned with a before and after graph showing their flow.
As for MPG, the injectors were Denso 700cc injectors headed into my 436whp MKIV Toyota Supra Turbo air/fuel processing monster. MPG range is 14 on track at WOT to 24 on highway, no boost cruising. MPG was not the goal.
I have no idea what to expect from a cleaning of the VX injectors and for the time begining I was not going to send them in until I know this car better. I posted this because the concept of truly cleaning and restoring injectors is best done off car and by a professional. You can count on them flowing within better than 1% of each other after cleaning. Depends on if or how bad they are going in.
I'm a big fan of having the injectors balanced and blueprinted. I had mine done at RC eng years ago. I didn't keep track of my mpg back then. If you've never had it done, you NEED to get it done as part of the maintenance. Your injectors are shooting a stream instead of spray. They're also not flowing evenly. Unfortunately the O2 sensor reads a sum of all four. Serviced injectors are better than brand new. They have a better spray pattern, they're capable of flowing more fuel, and they flow evenly resulting in a smoother running engine with less variance in air fuel ratio.
If you don't want any downtime you can go to the junkyard and get an extra set of injectors. They come off with a 10mm and a pick. Most Civics use 190CC injectors (DX, VX, CX, LX). The VTEC engines and twin cam engines use 240CC injectors. But be sure to get the same OBD generation as your car. I would get at least six and tell them to send you back the best four.
It was cheaper for me the get the manifold welded. It is complete fixed, the car does not search for idle anymore since the manifold is fixed. NO OTHER PROBLEMS ON THE CAR. It runs perfectly fine........ last fill up.... 33mpg.... i think im at the end with this car... im really really really sick of it by now..
Full tune up (filters,wires,plugs, water pump, timing belt, all liquids changed)
New bearings in tranny,
Car drives smooth and perfect.. BUT I STILL PULL ONLY 33MPG!
Im thinking of just cutting my lost and selling the thing.. i dont drive this car hard.. im always under 3k and i have a light foot... ac is always on but still..(in ca its hot) my goal was only for 40mpg and i still cant hit that in a car everyone else is doing fine in mid 40s