Im getting about 18 mpg hwy and about 14 city in my 1999 Ford Ranger 2.5l. I know driving habits can be the biggest influence on gas mileage, but I drove between 65-75 on the freeway on a long drive recently. I am unhappy with how much this is seeing that it is only a four-cylinder. Also a side note is the engine is freshly rebuilt and only has 1800 miles on the rebuild. But I am getting the same mileage I was getting before the rebuild. Thank you for any suggestions.

 

For best MPG engine coolant needs to be at/above 190degF, thermostat should be 192 or 195degF model, not 180degF

Check fuel filter connections for gas smell also fuel rail and around injector o-rings, just run fingers around and then smell for gas smell.

Pull a couple of spark plugs, should still be white or very very light brown color.
Darker would indicate Rich Fuel mix
That can be caused by False Lean at O2 sensor, an exhaust manifold leak will cause that.
Also make sure O2 sensor is tight, loose O2 causes False Lean
O2 sensors last about 150k miles, when they get older they also cause False Lean, so MPG will go down.

You can get a Bluetooth OBD2 reader
They run about $30
These plug into ANY, 1995 and newer, vehicle's OBD2 plug in.
You can then connect to them wirelessly with any Bluetooth smart phone or tablet.
You can then view codes of course, but also Live Data while driving, to see what fuel trims the computer is using.
Also what temp the coolant is running at.

2.5l should be above 20MPG at the least

 

I have a 192 degree thermostat and the temp gauge is right in the middle so I think it is running at the right temp. I will take a look at the spark plugs to see if the engine is running lean or not. Thanks

 

Forgot to update but I pulled the plugs and they are all still white. Im lost on what is wrong. I have since then replaced the IAC and the TPS and saw a significant change in the idle quality but no change in mileage. Im not sure what else to do. I have checked for vacuum leaks and have found none. Thanks for any suggestions

 

If plugs show no sign of Rich running then you are leaking the fuel, check fuel rail and injectors, fuel would evaporate fairly quickly if leaking there, also any connections, i.e. fuel filter, just run fingers around connections and injectors and smell for fuel.

Top of fuel tank is hard to get to but you could have a leak there.

If possible rent/get a fuel pressure gauge and hook it up, start engine then shut engine off, '99 should have 60-70psi fuel pressure, and it should hold that pressure for MONTHS, not hours, days or weeks, MONTHS.
This could show you if do have a leak or you don't

 

Okay I will try to get ahold of a fuel pressure gauge this weekend

 

Was playing with my OBD2 reader this morning going to work.

I have a 01 2.5L 2WD Reg Cab



Wayne

 

Checked the fuel pressure today and it is steady at 65 psi when it runs but drops to 20 as soon it shuts off. I hooked up an air compressor to blow air into the system and it's blowing out the gas tank. Would this cause bad gas mileage because it's not leaving the system just going back into the tank. If the psi is constant 65 shouldn't it run fine and have factory gas mileage

 

evaporative canister is pooched

evap purge valve is jammed open ( possibly )

 

Check valve on pump is bad if air pressure from the fuel rail was going back into the tank.

And yes this would not be the bad MPG issue.

Yes, it should run fine with any fuel pressure above 50psi, so outside of possible slow starting it should run fine.

 

he should replace the evap purge valve to be sure

considering the vehicles age , i know i would if my pickup was that old

 

Any other ideas as to why it runs rough and gets bad gas mileage?

 

have you ever replaced the oxygen sensors on your pick-em-up truck

try running a few tanks of 91 octane fuel ( without ethanol ) added

your truck`s computer was never programmed to read ethanol blended exhaust gases

it may be the ethanol blended fuel that is causing the issue