Honda VX CA emissions and MPG

[GasSavers_Whitey]

Great to find a site focused on MPG.
I have just bought a 1992 Honda Civic VX hoping for some great gas milage.
After putting the stock muffler back on the car from the "can" that came on it. It ran better. I didn't have to pump the accelerator to start it for one.
I left the big chrome intake pipe and cone filter the car came with on for a couple of tanks and seemed to range in the 35mpg to 40. This is about 20% city and 80% mild hilly puget sound driving.
I liked the low end appearance of power and smooth acceleration
at the beging of every shift.
I have since put the stock air intake system back on and seem to be getting 39-42 mpg with the same ratio of town and county
driving. Hmmm I wonder. where is that 48-55 mpg I read about.
Whoops! Its a califoria car now up here in Washington state.
Checking into things I've found it's rated for 44-51 MPG or so.
I have to questions to put out there for feed back.
Oh, I do have a roof rack with fairing and I'm guessing that will rob 2 MPG. Most highway driving is 55-65 MPH.

So 1st question. Is it possible to remove the california emmissions from this D15Z1 VTEC-e engine. I'm all about good emissions but also want great MPG. I feel this car is so much better than the national average I can live with it for now.
If it is possible is it pretty simple. I'm a decent driveway mechanic.

2nd question. The engine light comes on decending down grades after 15-20 seconds- intermittantly of course. I've heard an O2 sensor is most likely the cause at the age of 136k on the car. These sensores are pricey. If I remove the CA emmisions I'd guess the sensor will be set off anyway, so why replace it.

Could I get more MPG removing the CA emissions or replacing an O2 Sensor.

Looking forword to your insights

Whitey

[Matt Timion]

Welcome Whitey...

So let's tackle your questions. my UNDERSTANDING is that there are two main differences between the CA VX and the non-CA VX. The CA VX actually had a 4-wire o2 sensor, while the non-CA has a 5 wire o2 sensor. You can verify this yourself by just counting the wires on your o2 sensor.

I've seen 5 wire o2 sensors for sale on ebay for $50. I've purchased one myself for $25. A new (after market) one costs around $160 from Napa.

The other main difference is the ECU. Swapping the ECUS with a non-CA version will enable the "lean burn" option that is left out of the CA model. Lean burn and wideband o2 sensors go hand in hand.

I would do a little research. I'll ask a friend of mine for more specifics.

Wiring up the new o2 sensor would be VERY easy to do. It would probably take about an hour if you're a slow-poke (like me) or less if you're experienced in wiring and whatnot. You can probably get a non-CA ECU for around $30 on ebay or through a racing site.

I'll get back to you on specifics.

[Bunger]

I've owned a california (or so I thought) Civic VX before, and it had a 5 wire (wideband) O2. This O2 is what allows the engine to run in the lean burn mode. But like Matt said, the ECU and O2 go together.

As far as removing the CA emmisions, don't bother. If anything you're looking at an EGR system, which is NOT easy to remove. I would just do tune up on it and replace the O2 sensor (even a 30k mile O2 will not yield you the same mileage as a brand new one will). Check first and find out what code its throwing before you do anything though. A broken EGR valve can really mess up your mileage, but my guess is that it's complaining about the O2 sensor or there is a leaky injector.

[Matt Timion]

FYI, even the non-CA version of the Civic VX had an EGR valve. I get to enjoy wiring that up on my car that doesn't have one. YAY!

[Matt Timion]

it has been confirmed. The only difference between the CA and non-CA is the o2 sensor and the ECU.

If your engine code is for a bad o2 sensor, this is the perfect opportunity to switch.

All that you'll need to do is get a 5 wire o2 connector (you can even use other connectors, free from the junkyard). you'll run one wire straight to the ECU, just make sure it's a shielded wire. Put the new ECU in there and you'll be good to go.

[Bunger]

Ahh ok, that makes sense then. Also, I believe the 5-wire O2 connector is the same as the large connector on an OBD1 Honda distributor.

[Matt Timion]

If it's an eight wire rectangular connector, then yes. I have a five wire o2 sensor but no connector. I found a 8 wire rectangular connector in the junkyard (i think it was obd1) and it fits.