I am the very proud owner of a 1990 Bronco EB 4x4 with 302 efi. I'm trying to run axle codes to see what gears I have. I'm getting 8 and 9 miles per gallon. Is this all I can expect? Will a computer chip help me at all? I'm running stock everything including tires and I have no lift. I love the Bronco, but man this thing is KILLING me at the pump. Can anyone tell me what to do to improve this or am I peeing in the wind? What are you guys getting with similar setups. Thanks in advance!!!

 

8 - 9 seems a bit low for the 302. What is the history of the vehicle? When was the last time it had a tuneup, air filter, etc... Has the mileage always been this bad, or has it been getting worse over a period of time?

 

Wow 8-9 ? Man that sucks! sorry............. I have an 88 and I get typically 13-15 most of the time. The only time I get down below 10mpg is when Im heavy on the gas pedal.

What type of driver are you ? Are you the type that likes to race off the line at red lights, and waits to take your foot off the pedal right before you have to stomp on your brakes ? Im not trying to sound like Im bashing you, but the way you drive can really increase or decrease your mileage you are getting.

Also, if you are in need of a tune-up, that would have alot to do with it also.

I just changed my fuel filter and i've noticed an increase of 3mpg alone!

 

To answer all questions...I'm not a hard driver at all. As a matter of fact, I've paid really good attention to my driving just to see if I could improve it by being careful. My engine in very fresh with only about 1500 miles. Everything is stock. My check engine light is NOT on, so I doubt that I could pull a code. I just put in a K&N and changed my throttle position sensor. Could things like O2 sensors affect mileage. If that was the case I think my check engine light would come on, right? The only thing I can think of is my gearing. What do you think? Is there a site that can tell about my Bronco decoding the VIN? I can't really say what the mileage was before because it ran so badly that I didn't drive it a lot. My number 8 piston had a chunk missing when we tore it down. When the new one was put in I changed all hoses, belts, plugs, wires, cap, rotor...EVERYTHING!!! Does my info help any? If there is any other helpful info you have, I would greatly appreciate it.

 

Other items to check would be the operation of the thermostat and correct temperature thermostat. Mine had to be 195 degree before mine would work in closed loop mode, 88 302EFI.

The oxygen sensor failing will make the fuel mixture too rich.

Both the engine cooling temperature, ECT, sensor and the intake air temperature, IAT, sensor play a major role in the fuel mixture. One or both of these may be bad. These can be checked before purchasing replacements.

The manifold absolute pressure, MAP, sensor could also be faulty or have a broken vacuum line.

The last thing that I can think of at the moment is the air injection thermactor valve at the back of the engine could be open or partially stuck open, may also be due to bad solenoid control valve. This allows air injected into the exhaust ports in the heads and the oxygen sensor detects this as a lean condition and the computer compensates with more fuel.

A service manual is help for trouble shooting the ECT, IAT, and the MAP sensors.

 

How do you check those things? I wonder if any of my sensors are bad. I think my thermostat is a little on the shady side. I want to change it but its freezing outside and I don't want to play with it in the cold

 

You can still have stored codes even if the CEL isn't on - not all codes trigger the light. To pull & clear them, read this page.

The Haynes manual tells how to test each sensor, and explains what they do & how they work. It's the best resource, but this site isn't too bad.

 

another thing is that new engines do take a few miles to wear in. After they're broke in, mileage usually increases 3-5 mpg.