I have had a ranger 4.0 ohv XLT 4x4 with stock 4.10 gear with 205 000km for a few month, i changed tires to 33 12.5 R15, however the difference was minimal.

On summer i average 13mpg, and on pretty cold weather i average 8-9mpg, mixed highway and city, and i try to be as careful as possible on throttle, i have to press throttle to 75%+ throttle to climb a 10% road and keep up 90kph, this winter i had check engine popping up 3 times, each time it was p0171 and only happend to pop up when it was very cold outside (-25-30c without windchill) otherwise no other check engine ever happend. I also noticed, on very cold weather, that my truck exhaust make a lot more white smoke than any other pick up truck out there, like twice. Im not surprised if the car behind me is blinded by it. Ive had maf, iac and throttle body cleaned, and new plugs, didnt help.
Engine idle fine but to about 800rpm when warm.
The engine feels weak and very slow for a 4.0.

Im starting to have enough of this engine, are they supposed to run like this?


One more thing, on summer at hot temps (30c+) the engine make a loud noise when engine temps reach around 200F, sounds comes from air intake.
What could this be? Could these make my issues?

 

Well to answer the original question yes that mileage is bad and not normal. I'll let others chime in about the other issues.

 

Yeah, thats by terrible.

But, did you recalibrate the speedo/odo for the larger tires?

 

Yes, MPG is off, with 200k miles there should be new O2 sensors installed, expected life for upstream O2 sensors is 100k, they tend to wear out Rich lowering MPG.
You just need to change the two Upstream O2 sensors, the downstream O2(after Cat converter) is just there to test if Cat is working, it doesn't effect MPG, although you may get Check Engine Light(CEL) after changing front O2 sensors, check the code, if it is for the downstream O2 then you will have to change that as well.

As far as the noise.
With engine cold
Loosen fan belt, remove it from crank shaft
Start engine, it is OK to run a cold engine for a couple of minutes without water pump, Battery Light will stay on, that is OK.

See if noise is gone, if so then you have a bearing going out on a pulley, or an alternator can make a whining noise if its starting to fail.
Spin each pulley(engine off now) and listen for roughness of bad bearing, don't forget idler and tensioner pulleys.
If noise is still there then you have an air leak in Plenum(big tube from air cleaner to intake), remove it and inspect it closely, leak could also be in air filter housing

 

Im using my ultragauge with adjusted speed.

 

I will try o2 sensor, thanks.

As for the noise, its all about the mix of pretty hot weather outside and engine, i have a ultragauge showing the engine temps, the noise start at 185-190, but quietly, but when engine reach 210-220, its beyond really loud like in the video, last time i heard these noise was last summer, on really hot temps outside. Engine temp still reach nearly 200F on winter but no sounds ever, someone told me it could be IAC? Its like the noise is coming from the intakje tube, not alternator or strap. I tried to remove the airbox and start engine with only the intake tube, noise still happen.

 

IAC Valve does have a breather to allow the valve to slide, it equalizes the pressure behind the valve.

With engine warmed up unplug the wire on the IAC Valve, this will cause the valve to close and engine RPMs will drop to 500, engine might stall, thats OK.
But see if the noise stops when IAC Valve is unplugged.
These are very easy to clean.

Good read here with pictures, the black cap is the breather: IAC valve cleaning thread (w/pics) - Ford Explorer and Ranger Forums "Serious Explorations"®

 

Thats the problem, i cant test it, because there wont be any noise at this seasons of the years, i can only hear this noise when its very hot outside + engine is at least 190F (Quiet noise) and 220F (LOUD noise), though i will try when sounds come back, actually im pretty sure the sounds started after i cleaned it.

However for now i really need to get that MPG back up, other than o2 sensor, what should i check?

 

I would get or rent an OBD II reader/scanner, and check the Fuel trims while driving.
I would expect you to get a Check engine light(CEL) running as rich as you are.

You can buy the Bluetooth OBD II readers that show on your smart phone or tablet, usually under $40, and they work on any vehicle sold in 1995 and later, so not a ranger thing or ford thing

If you are not running rich then you have a fuel leak.

 

I have a fuel trim on my ultragauge, for bank 1 and 2. I dont have any CEL. I think my ultragauge can also show fuel pressure

What should i expect to see on my ultragauge if there is a problem?

 

There are two fuel trims, STFT(short term) and LTFT(long term)

Computer works out fuel trims like this:
When engine starts the MAF(mass air flow) sensor tells computer how much air is coming into the engine.
Computer needs to mix 14 parts air with 1 part fuel, 14:1 ratio

The MAF data sets the 0 in the fuel trim, this is important because the 0 changes with RPM because engine is, of course, pulling in more air, so it is a "floating 0".
Computer uses preset 14:1 mix table in memory until O2 sensors come online.
O2 sensors can't work until they reach 650degF so it takes a few minutes before they can provide Oxygen content in exhaust data.
After this warm up the fuel trims can be read and make sense.

Computer reads MAF data and adds 14:1 fuel
If there is too much Oxygen in the exhaust(O2 data) computer opens fuel injectors longer(pulse width)
This shows as +1 on STFT
Still too much Oxygen, then +2, and so on, at around +20 the computer will set a Lean Code because it is past its preset limit, it is having to add too much fuel if MAF data is correct(this happens with vacuum leak because not all the air is coming in thru the MAF sensor)

If there is not enough Oxygen in the exhaust(O2 data) the computer shortens the fuel injector open time.
This shows as -1 on STFT, and so on up to -20 where you get a Rich code.

When engine is running the STFT will change very fast, that is the computer varying the injector Pulse Width to hover around the 0 mark.
In a perfect world you should see cycling from -5 to +5 while driving
When idling +3 to +7 is normal since idle needs to be a little richer.

As a vehicle gets older the parameters change, fuel pressure can lose a few PSI so injectors need to be open longer to get the same amount of fuel, so that could add +5 to trims.
O2 sensors get older and coated with exhaust so can cause trims to vary.

Generally -10 to +10 ranges are not a concern, when it gets above that there could be a problem starting.
Time to clean MAF and/or replace O2 sensors

LTFT is used by computer when O2 sensors are off line, as said engine parameters change with time so the pre-set memory tables from the factory need to be modified for that, thats what LTFT is for.
It gives continuity for fuel use for current engine state.

 

Alright thanks, ill check this out. :)

 

I average from -5 to +5 on both bank, but more around 0 to -5. So i guess my o2 sensor are ok? Or it may look ok but the dirt just hide the bad?

 

Long shot for two O2 sensors to fail identically.

My guess is engine is running as economically as possible with those fuel trims.

So poor MPG lies somewhere else, i.e. have you looked behind the truck? and didn't notice a 1,000lbs trailer there?

LOL, kidding

You could have a fuel leak, might be worth while to check fuel pressure, but more specifically check if it starts to drop after key is off, it shouldn't, fuel system will hold pressure for months.
Could be filler hose is leaking when tank is full and when cornering.

Could be ultra gauge isn't reporting distance correctly.

Dragging brakes

How does it roll on flat ground?

 

How can i check the pressure?

Also i have calibrated my ultragauge speed for the bigger tire, as for the brake, i dont think they are dragging, however, when i let my steering go, my truck slighty does turn to left.

What do yo mean roll on flat ground?

 

Go to a flat parking lot, shut off engine put it in neutral and push the truck, you will feel if it is dragging anywhere.

You get/rent a fuel pressure gauge, there is a schrader valve(looks like a tires air valve) on the fuel rail, you hook up the pressure gauge to that and start engine.
2000 Ranger should run at 65psi, after shutting down engine it should hold above 50psi for hours.

You most likely need an alignment with the larger tires and yes that does reduces MPG but not by the amount you have mentioned.
It will also wear out the front tires faster.

With your fuel trim numbers and no obvious signs of rich running, i.e. grey smoke out the tail pipe or blackish spark plugs, I would move on to other causes.

Occam's Razor is a problem solving principle.
Basically it says when there is a problem the best solution will be "the one with the fewest assumptions"
Or "the simplest solution is usually the correct one".
The razor part is that you "cut" away/remove possible solutions as much as possible, and whatever is left, no matter how improbable is the solution, basically Sherlock Holmes, lol.

In your case the engine isn't showing any signs of burning extra fuel, so it isn't.
So either the fuel is leaking out
Or the method of measuring MPG is flawed
That is all that is left

 

Have you compared the ultragauge mileage traveled with a GPS unit, or GPS app on your phone?

 

I forgot to mention that there was sometime a smell of gas when i get ouf of the truck, but could only smell it on summer. So if i had a leak, i would see it on fuel pressure right?

 

Yes i have calibrated the new speed with a gps unit.

Just to keep up 50kph, i get an instant MPG of more or less 10MPG, about 13-14mpg to keep up 90kph, both on flat ground. I take about 4 liter of fuel to travel around 20km.

 

I have never set up an ultra gauge, but it can not "know" MPG just from being hooked up and setting tires size.
You would need to first "tell it" what the MPG is, or give it a known miles traveled gallons used starting point.
OBD II info has nothing that tells a gauge how many gallons/liters are being used per hour or mile

 

Just to completely rule out a scangauge error can you completely fill up your tank, then use a gps unit to track miles, and do the simple miles divided by gallons when you fill back up? Not trying to insult your intelligence or anything, but this way we can completely rule out a scangauge mileage/mpg error.

 

Sorry I miss the "I smelled gas in the summer" part.

Then you for sure have a leak.

What you smell are aromatic hydrocarbons from gasoline evaporating, and that doesn't happen as much when it is cold.
The fuel system(lines) runs under the drivers seat inside the frame, fuel filter is there.
Also the filler is on the drivers side.

Yes, a fuel pressure test would tell you if there was a leak between Fuel pump and Fuel rail.
But not inside the fuel tank, i.e. filler/vent hose.

 

For those curious in here, when you set up an ultragauge for mpg. The unit asks for tank size then you can fill the truck and press "fill up". After a few fill ups it self adjusts and gets accurate. I Forget if you are asked engine size but I do know you can program axle gearing and possibly tire size.

I used my SCT to reprogram tire size when I got it and them.

 

Alright thanks guy

I will try to reprogram the ultragauge when i can afford a complete refill. I was asked for engine size, but not axle.

Then i will get the fuel pressure checked, and hose/tank, and change fuel filter while at it.

Another detail, if it matter, is the white smoke coming from exhaust at very cold weather, i know every vehicle does it, but mine does it twice as much as any other pick up ive seen, even when engine is warm, im pretty sure i will be blinding the car behind me if hes too close.

Also my truck Idle at around 850 rpm when warm, on ultragauge, and 1000-1100 on dash gauge.

 

I could be wrong about the axle thing, it's been like 4 years since I programed mine.

I hate to touch on this but you have a lot of miles, you might have the staring of a blown head gasket or even long gone. Are you going through coolant?