1992 Honda Civic VX Lean Burn Shutoff?

[Dev]

Hello Ecomodders!

A few months ago I purchased a faded red 1992 Honda Civic VX with 370,000+ miles on it as a vehicle that would get great fuel economy without doing anything to it besides a simple tune up and cleaning. I've had the car for awhile now and i've loved the fuel economy i've been getting.

I bought a vacuum gauge for it and I noticed that whenever the vacuum gauge hits 0, it starts to speed up alot faster. I assume this is the ECU changing the fuel mixture from a lean mixture, to a stoichiometric mixture. (If i'm incorrect, please explain why)

As the title of the thread says, I would like to make a switch that can shut lean burn off. This is my daily driver, and I do like to go on backroad cruises and have full power, but I also like to save my gas when driving from point A to point B. When I'm on a backroad, I don't care what I'm getting for fuel economy. I don't like when the vacuum gauge reads 5, and when i go to push the throttle more and it goes to 0, that speeds up really quickly. ( I assume the ECU is going back and forth from a lean mixture and a stoich mixture. It's just very annoying when all I want is power )

I know there are wires that lead from the O2 sensor that go to the ECU, and I'm wondering if I made a switch that stopped some signal going to the ECU, that the computer would just continue to run a stoich mixture?

Here is a link (http ://technet.ff-squad.com/wiring.obd1. htm) that shows ECU wiring and stuff, Connector D has the Lean Burn o2 wires, if anyone knows what needs to be switched, cut, ect. please let me know! Would love to make a DIY post for anyone else who may want this mod on their VX.

[JRMichler]

Most of the time, your engine is running a stoichiometric fuel mixture. At stoichiometric, you get gas mileage, reasonable power, and good emissions.

Some cars will go into lean burn under certain conditions. Those conditions include low throttle (high vacuum). Gas mileage improves, power drops, and emissions get worse.

Most cars dump in extra fuel at wide open throttle (zero vacuum). Gas mileage gets really bad, power increases, and emissions get worse. Since the wide open throttle fuel enrichment is a step change, you feel it as a sudden increase in power.

You could readjust the WOT switch to keep it in fuel enrichment mode to eliminate the power jump when you hit WOT. In that case, expect the following:

Bad gas mileage.
Need to change oil more often due to unburned fuel contamination.
May kill the catalytic converter.
Carboned up spark plugs.

Or just stomp the gas pedal when you want full power. Then you won't notice the WOT fuel enrichment power jump.

[oil pan 4]

I wouldn't worry about the carbon on the spark plugs.
I run a kind of mad max tune where its lean all the time, except when I floor it. Then the air fuel ratio goes down to about 12:1.
Before that when I first got the suburban it was running the "idiot red neck tune" running so rich it wouldn't read on my air fuel meter a lot of the time and was getting half the fuel mileage it does now.
The plugs were fouled pretty good. I was going to change them when I got the tuning nailed down, but then I forgot.
Last week I pulled some of them and found that the lean burn had burned all the carbon off the ceramic insulator so I put them back in.

[Dev]

Thank you guys for input! I did a little thinking and some more research, found out what wire (PIN D-8, LAF Sensor VS+) on the ECU was the lean burn turn on switch ( I guess you could call it that. lol ) and I just cut it, extended the wire to a switch on the dash, and ran a wire back to the ECU.

I won't be running it out of lean burn all the time, and if someone plans on doing this, you should change the spark plugs to a plug that runs cooler.

If someone ever does this mod, it takes 4 seconds to change over to a stoich mixture, and if you turn lean burn back on, you have to shut the vehicle off and turn it back on. This resets the ECU and enables lean burn again. Maybe I can make a DIY guide and post it!

Thanks again for everyones comments. It was nice to look at it from different angles!