O2 sensor for 90 yj with 4bbl carb

[msubulldog]

My O2 sensor has been disconnected and I was wondering if this has anything to do with my jeep getting only 10 mpg. I do have a 4bbl, 600 cfm Edelbrock carb on a 6cyl and 33" tires, but I got 10 mpg with the original carb. If I jetted the carb down to like 400-450, or whatever, and connected the O2 sensor, would that help? I don't know if the O2 sensor would work the same with me having the bigger carb. What do ya'll think?

[Busted Knuckle Racing]

yeah, it could be the cause. The O2 sensor is in the exhaust manifold so it will monitor the exhaust gases no matter what carb you have on there. You may be running too rich and with no O2 sensor, your computer doesn't know.
How an O2 sensor works:
An Oxygen sensor is a chemical generator. It is constantly making
a comparison between the Oxygen inside the exhaust manifold and air
outside the engine. If this comparison shows little or no
Oxygen in the exhaust manifold, a voltage is generated. The
output of the sensor is usually between 0 and 1.1 volts. All
spark combustion engines need the proper air fuel ratio to
operate correctly. For gasoline this is 14.7 parts of air to one
part of fuel. When the engine has more fuel than needed, all
available Oxygen is consumed in the cylinder and gasses leaving
through the exhaust contain almost no Oxygen. This sends out a
voltage greater than 0.45 volts. If the engine is running lean,
all fuel is burned, and the extra Oxygen leaves the cylinder and
flows into the exhaust. In this case, the sensor voltage goes
lower than 0.45 volts. Usually the output range seen seen is
0.2 to 0.7 volts.

What does the O2 sensor do?

It is the primary measurement device for the fuel control computer
in your car to know if the engine is too rich or too lean. The
O2 sensor is active anytime it is hot enough, but the computer
only uses this information in the closed loop mode. Closed loop
is the operating mode where all engine control sensors including
the Oxygen sensor are used to get best fuel economy, lowest
emissions, and good power.


Try just connecting the O2 sensor and see if it helps.

[rsmith]

If it has an Edelbrock carb I am assuming it did not come from the factory that way. If that be the case, then the O2 sensor has no control over the air/fuel mixture.

I have run an Edelbrock 600 and it is great and responsive, but it did not get the best mileage. Jetting down may help, but I would recommend running a Quadrajet that is better off-road and more fuel conservative.

I am running a 2 bbl Ford Motorcraft carb on a 4 bbl intake on my 258 straight 6 in my CJ7 with 31" tires and 3:43 gears and getting 16 mpg at best. Jeeps just aren't real famous for great gas mileage.

[Busted Knuckle Racing]

rsmith said:

If it has an Edelbrock carb I am assuming it did not come from the factory that way. If that be the case, then the O2 sensor has no control over the air/fuel mixture.

good point Rob