Bad MPG. Is cat clogged?

[ford4wd08]

What should be temperature outside cat? Will be check tomorrow

That I can't answer off the top of my head, but usually if they clog bad enough, they will glow hot.

 

[Pauls14]

That I can't answer off the top of my head, but usually if they clog bad enough, they will glow hot.

Ok, thanks. Will write when check

 

[Curious Hound]

Even healthy, they get too hot to touch.

 

[gaz]

Pauls14,

If you have verified the "alleged" tune up to be actual, here's what I would do:

1) complete the tune up with new engine oil, transmission and axle fluids, engine coolant flush/fill and verify your tire pressure.

If mileage is still crap,

2) have your valves checked and subsequent valve job performed by a competent, trusted machinist.

If mileage is still crap,

3) look at your valve train components. The rockers and push rod wear are known issues on these power plants. Also, you may want to consider the use of adjustable push rods so that you can maintain proper valve geometry in the future.

*Deltacam of Tacoma Wa is the only company that refurbished worn rockers and adds a hardened insert.
* Smith Brother's will make you a custom set of (adjustable or non-adjustable) push rods for your engine, ensuring the highest possible efficiency from your lifters and valves.

There are more moves to increase your 4.0L's fuel economy but that's were I'd start.

 

[gw33gp]

I haven't seen anything about O2 sensors being replaced. They can start going bad and cause poor mpg without throwing a code. I know there is a way to test O2 sensors but I don't remember what it is.

 

[Pauls14]

I haven't seen anything about O2 sensors being replaced. They can start going bad and cause poor mpg without throwing a code. I know there is a way to test O2 sensors but I don't remember what it is.

I can check voltage, thanks. I’ll try too

 

[Uncle Gump]

Get the vehicle warmed up and get it out on the freeway. Will the truck get to and maintain highway speeds? Will it accelerate from highway speeds? If you answer yes to those questions... the cat is not plugged.

Now remember... rich fuel mixtures generate additional heat in the cats... because the cats are working double time trying to clean the exhaust. If you're rich and you don't fix it... it will certainly lead to the cats melting down.

I would pull the plugs and read them. Maybe you have a leaky injector(s). Do you even know what brand plugs you have installed? Do you know what the fuel pressure is? Does the engine start hard after warming up? Is your fuel pressure regulator leaking?

 

[Pauls14]

Get the vehicle warmed up and get it out on the freeway. Will the truck get to and maintain highway speeds? Will it accelerate from highway speeds? If you answer yes to those questions... the cat is not plugged.

Now remember... rich fuel mixtures generate additional heat in the cats... because the cats are working double time trying to clean the exhaust. If you're rich and you don't fix it... it will certainly lead to the cats melting down.

I would pull the plugs and read them. Maybe you have a leaky injector(s). Do you even know what brand plugs you have installed? Do you know what the fuel pressure is? Does the engine start hard after warming up? Is your fuel pressure regulator leaking?

Truck runs good on highway. About plugs don’t know. Engine starts easy after warming up. I guess if leak I will feeling smell. But smell only burn dirty.

 

[Uncle Gump]

In my experience... the cat(s) are probably not plugged. Because when plugged... the vehicle will experience a loss of power.

Logic also tells me with that kind of fuel mileage there is something wrong. Most things causing a rich condition will set a DTC... and/or have a drivability issue.

Does the check engine light illuminate with the key ON engine OFF?

Pull the plugs and see if they're fuel fouled... and see what brand they are. If they are anything but Motorcraft or Autolites... throw them in the trash can and buy the proper plug in either Motorcraft or Autolite.

I would also pull the vacuum line off the fuel pressure regulator and see if there is fuel in the line. If there is... the regulator is junk and needs to be replaced. I would still put a fuel pressure gauge on the system and check fuel pressure... and also see how fast it bleeds off pressure after you shut the engine off.

 

[Pauls14]

In my experience... the cat(s) are probably not plugged. Because when plugged... the vehicle will experience a loss of power.

Logic also tells me with that kind of fuel mileage there is something wrong. Most things causing a rich condition will set a DTC... and/or have a drivability issue.

Does the check engine light illuminate with the key ON engine OFF?

Pull the plugs and see if they're fuel fouled... and see what brand they are. If they are anything but Motorcraft or Autolites... throw them in the trash can and buy the proper plug in either Motorcraft or Autolite.

I would also pull the vacuum line off the fuel pressure regulator and see if there is fuel in the line. If there is... the regulator is junk and needs to be replaced. I would still put a fuel pressure gauge on the system and check fuel pressure... and also see how fast it bleeds off pressure after you shut the engine off.

Yes, when I turn on, check engine light. Can I buy chipset gauge pressure? ( I saw on Amazon around 20$).

 

[Pauls14]

In my experience... the cat(s) are probably not plugged. Because when plugged... the vehicle will experience a loss of power.

Logic also tells me with that kind of fuel mileage there is something wrong. Most things causing a rich condition will set a DTC... and/or have a drivability issue.

Does the check engine light illuminate with the key ON engine OFF?

Pull the plugs and see if they're fuel fouled... and see what brand they are. If they are anything but Motorcraft or Autolites... throw them in the trash can and buy the proper plug in either Motorcraft or Autolite.

I would also pull the vacuum line off the fuel pressure regulator and see if there is fuel in the line. If there is... the regulator is junk and needs to be replaced. I would still put a fuel pressure gauge on the system and check fuel pressure... and also see how fast it bleeds off pressure after you shut the engine off.

About regulator. I think if it broken, he couldn’t gives more than usual quantity fuel. Because fuel injectors give fuel. If it so much fuel, it will move fuel in back line to tank.

 

[Curious Hound]

About regulator. I think if it broken, he couldn’t gives more than usual quantity fuel. Because fuel injectors give fuel. If it so much fuel, it will move fuel in back line to tank.

When the fuel pressure regulator fails, it leaks fuel into the vacuum line that actuates it. That leaked fuel is sucked into the intake manifold and is added to the fuel that the injectors put into the cylinders. This makes the engine run rich.

 

[Pauls14]

When the fuel pressure regulator fails, it leaks fuel into the vacuum line that actuates it. That leaked fuel is sucked into the intake manifold and is added to the fuel that the injectors put into the cylinders. This makes the engine run rich.

I got it, thanks.

 

[Pauls14]

In my experience... the cat(s) are probably not plugged. Because when plugged... the vehicle will experience a loss of power.

Logic also tells me with that kind of fuel mileage there is something wrong. Most things causing a rich condition will set a DTC... and/or have a drivability issue.

Does the check engine light illuminate with the key ON engine OFF?

Pull the plugs and see if they're fuel fouled... and see what brand they are. If they are anything but Motorcraft or Autolites... throw them in the trash can and buy the proper plug in either Motorcraft or Autolite.

I would also pull the vacuum line off the fuel pressure regulator and see if there is fuel in the line. If there is... the regulator is junk and needs to be replaced. I would still put a fuel pressure gauge on the system and check fuel pressure... and also see how fast it bleeds off pressure after you shut the engine off.

Today I’ve tried to find fuel pressure regulator and check vacuum line , but could not. Then i read in web about. There is only fuel sensor under hood (only too holes and connector), I guess if it doesn’t work I will see check engine. Second fuel pressure regulator or damper in the tank with fuel pump.
Also I saw on 4.0 OHV Explorer, there damper under intake in the fuel rail. (I have to take it apart, but I am not sure in ranger same or not)

 

[ratdude747]

Today I’ve tried to find fuel pressure regulator and check vacuum line , but could not. Then i read in web about. There is only fuel sensor under hood (only too holes and connector), I guess if it doesn’t work I will see check engine. Second fuel pressure regulator or damper in the tank with fuel pump.
Also I saw on 4.0 OHV Explorer, there damper under intake in the fuel rail. (I have to take it apart, but I am not sure in ranger same or not)

It's on the Passenger side of the fuel rail (which is part of the upper intake stack). Hidden under/behind the throttle/cruise cable retainer assembly. You're looking for a red hard vacuum line.