10mpg?

[Granger]

Just bought this 86 4x4 v6 ranger. It had a high idle, so i changed the iac and that brought the idle back down to 800. However I have been getting about 10-14mpg, I know that this is not right. I had an 83 f150 with the 4.9 that got better gas mileage.

What are some things that I need to check first? are there any common issues with the 2.9's gas mileage?

 

[RonD]

The 1986 2.9l ranger was listed at 16-18MPG

Fuel injected engines can't use a standard choke setup so to get a cold engine to run correctly they needed something that could tell the engine computer the temperature of the engine so it could open injectors longer to run engine rich until it warmed up.
They invented the ECT sensor, Engine Coolant Temp sensor, sound familiar, lol.
They renamed the dash board gauge sender, but they did add an extra wire

The ECT tells the computer if the engine is cold or warm, if this sensor has a problem engine could run poorly when cold, not rich enough, or run fine cold but suck down the fuel when warm because it is running rich all the time.
The ECT is easy to test with an OHM meter, it is a standard resistance sensor.
The OHMs change as the sensor is warmed and cooled.

The ECT sensor and gauge sender are usually located near each other and near the upper rad hose connection on the engine.
Gauge sender has 1 wire
ECT sensor has 2 wires

Test ECT with engine cold then while engine warms up; ECTs come in two "flavors", low OHMs cold-high OHMs warm, and high OHMs cold-low OHMs warm.
You are watching to see if OHMs change and it should change quite a bit.

Do not just replace this sensor, it might not be the problem, it just "could" be the problem.

Do you have a Check engine light(CEL) on?
Does your CEL work when you turn on the key?
Some sellers disable the CEL bulb

A bad ECT wouldn't set the CEL on, this is the only sensor that tells the computer if engine is cold or warm, so it has nothing to compare it to, a disconnected ECT(or bad wire) might turn on the CEL.

 

[Nutz-N-Boltz]

Check for vacuum leak, check fuel pump pressure, check for fuel in regulator vacuum line.... Just a couple common things.

 

[Canndspam]

Last time I got mpgs like that it was cuz the meth heads down the road had siphoned my gas.

 

[Canndspam]

For a more helpful answer, I've had a number of different sensors go bad and negatively affect my gas mileage. ECT was one of them, as well as the EGR valve position sensor, the EGR valve itself being clogged, the air charge temp sensor, and the O2 sensor. Running the codes told me all of them with the exception of the O2 sensor. For that one it didn't say that the sensor was bad, it just said that it was sensing that the system was lean, so it was dumping gas to compensate. However, none of those caused my mileage to drop as drastically as you're talking about.