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  • OT Fuel management computers and MPG

    On another forum, http://www.fordrangerforum.com/, there is frequent discussions about lousy fuel economy of Ford's 4.0 SOHC V6. A lot of members are kids jacking around with stuff they know nothing about. (I don't know much, but I have a sneaking suspicion not to jack around with stuff I know nothing about and have had fairly good results). I have one of these engines and mileage is lousy (14-16 mpg mixed driving). The latest complaint on the forum was some guy getting 8-9 mpg. http://www.fordrangerforum.com/4-0-s...0-8-9-mpg.html

    My question. Back in the day with a poorly tuned carburetor, the mixture could get overly rich and dump raw gas out the exhaust resulting in poor mileage. Also a poor spark would send gas through unburned. Today with computer controlled injectors and oxygen sensors, I would expect the mixture to be correct or an error code displayed. Looks like a poor spark would also show up in the O2 in the exhaust. If my assumption is correct it sure rules out a lot of old troubleshooting suggestions - dirty injectors, plugs, plug wires, etc. Am I thinking correctly?

  • #2
    9MPG? Is his motor even turning over or does it just use the force of the exhaust gases to move it down the highway?
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      On the back end of the engine is a vacuum tree that controls the fuel pressure regulator. On that tree is a stub with a plastic cap on it. If that cap is removed or leaking the fuel pressure regulator stops working and the pressure goes to maximum all the time. This causes the engine to run at full rich which gives better cooling and a little more power but kicks the s**t out of the gas mileage.
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      • #4
        This is a classic case of trying to run an engine too lean, and achieving poor to lousy gas mileage in the trade-off. Ford has been inundated with poor performance, lousy fuel economy, and marginal reliability complaints ever since they introduced the 4.0L SOHC engine. At the Proving Ground, one had to open the hood to determine if the powerplant was a side-valve four-cylinder or a SOHC V-6. Of course, the four-cylinder got much better gas mileage.

        You should have been suspicious when you did your first fill-up and it took 30 gallons to top it off.

        The boys at Ford really had their "thinking caps" on when this one came out.
        I suppose you know that both cylinder heads are identical, and replacing the timing chain cassette on the left bank requires removing the transmission...or pulling the engine. (Ford recommends replacing the timing chain cassettes at 70K miles, BTW).

        To make matters worse, Ford decided to gear the truck tall so that it would run relatively quiet at highway speeds. Transmission calibration could have been more carefully chosen, also. But, Ford was too busy replacing them to bother with any form of recalibrating.(LT does actually stand for "light Duty"in the transmissions' identifying numbers...It should be rebadged as "real light duty" instead)

        If this engine doesn't drive the last nail in the Ranger's coffin, nothing else will. Ford's idea of an April Fool's Joke that keeps on giving.
        Last edited by saltmine; 04-01-2011, 12:03 PM.
        No good deed goes unpunished.

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        • #5
          I would highly suspect that either Ford geared these extremely poorly, or calibrated the engine to the vehicle extremely poorly, but couldnt tell you which without more information.

          If it has a fairly high rear ratio (<3.00) then I would check the trans ratios as well to make sure nothing is too strange there ie, that the rearend isnt driving a million rpm to make the same wheel speed. In the case of automatics I would also check the shift points. If you feather the gas pedal, does it shift at above 3000 rpm?

          The case of poor calibration is very difficult to determine, easiest done with a laptop viewing the calibration flash files in the ecm. Basically what would happen in this case is the engine is tuned to run rich to the point of giving the same power, but poor fuel economy.

          Modern auto engines for about the last ten years or so typically run extremely lean, close to the edge of detonation the majority of the time (which is why you have knock sensors on engines). This improves fuel economy and emissions quite nicely as well, but has little affect on power due to the instanteous response of modern direct injection systems. Generally, the parameters inside your ecm are fairly well planned and executed to give a good mix of power, economy, and emissions, and unless you have a serious need to, I would seriously think twice about letting anybody tinker with them, unless you happen to know someone who does this in a very controlled scientific manner. Personally i have never known anybody outside of the OEMs design staff that I trusted to do this. Shops that claim to specialize in tuning ecms typically have a trial and error approach and cannot take into account all the little factors that affect engine durability, so visit them with caution.

          So basically, unless you can change the gearing to solve the problem, youre stuck with the mileage unless you want to risk hurting your engine.
          "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

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          • #6
            You are correct that a drop in mileage is normally caused by an injector, o2 sensor, FPR, etc.

            I have had to change a FPR on a ranger once because the diaphragm was leaking fuel into the vacuum line. The 4.0 is a piss poor motor all around and should never been released.

            If you want mileage, power, and reliability get a honda. American companies are all just playing catch up to the imports and are half assing their way along.
            Andy

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            • #7
              Originally posted by saltmine
              This is a classic case of trying to run an engine too lean, and achieving poor to lousy gas mileage in the trade-off. Ford has been inundated with poor performance, lousy fuel economy, and marginal reliability complaints ever since they introduced the 4.0L SOHC engine. At the Proving Ground, one had to open the hood to determine if the powerplant was a side-valve four-cylinder or a SOHC V-6. Of course, the four-cylinder got much better gas mileage.

              You should have been suspicious when you did your first fill-up and it took 30 gallons to top it off.

              The boys at Ford really had their "thinking caps" on when this one came out.
              I suppose you know that both cylinder heads are identical, and replacing the timing chain cassette on the left bank requires removing the transmission...or pulling the engine. (Ford recommends replacing the timing chain cassettes at 70K miles, BTW).

              To make matters worse, Ford decided to gear the truck tall so that it would run relatively quiet at highway speeds. Transmission calibration could have been more carefully chosen, also. But, Ford was too busy replacing them to bother with any form of recalibrating.(LT does actually stand for "light Duty"in the transmissions' identifying numbers...It should be rebadged as "real light duty" instead)

              If this engine doesn't drive the last nail in the Ranger's coffin, nothing else will. Ford's idea of an April Fool's Joke that keeps on giving.

              Sounds like you really have a grudge for some reason.

              A few facts:
              Fuel capacity is 17 to 20.3 for my 2004 not 30 gal.
              I checked Ford's recommended maintenance and there was nothing about timing chain replacement to the end of the schedule at 150,000 miles.

              And some thoughts and observations:
              There seems to be a lot of Rangers and explorers with 170k miles that haven't had the engines apart. If the engine needs to come out after that for a timing chain, I wouldn't like it but that's still pretty good service and it won't be mine when it has that many miles.

              There don't seem to be many rebuilders doing that engine and given the number on the road there must not be much of a market for them.

              My local wrench tells me that some timing chain failures are attributed to improper oil filters without or failing drainback valves. Cam chain tensioners need oil pressure immediately on startup to prevent chain slap and damage.

              Regarding the gearing, my first car had a two speed automatic, the next one a three and this Ranger has a 4. Don't know why optimizing the gear ratio would be that much of a problem.

              You lost me on the test track comparison of the 4.0 and the model A engine on the test track but that's OK.

              I don't like the lousy mileage after driving a 2.5 2 wd for years but I need a truck and I need a 4x4 to get out of here in the winter and they don't make a 4 cyl 4x4 Ranger and I don't drive that many miles a year.

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              • #8
                I have a 2009 ext cab 4x4 ranger, and i cant remember exactly what im getting for milage, but i think its around 15mpg, which is 6mpg below fords rating for highway. One of my friends just bought a 2010 about 6 months ago and he says he cant believe how much he has to fill that thing up, but I dont know if he has ever done the calculations. He also got a tonneau cover a couple months ago and says his milage has gotten a little better than with an empty box.

                Just for the record, i have the V6, 5-speed auto with the 4.10 axle gears. I also have the P255/70R16 tires.

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                • #9
                  One would think that with them redesigning the ENTIRE CAR every year, to be completely part incompatable with every car that ever came before it, And charge $20,000~$40,000 for a BASIC car, they might of made a few improvements in the past.. 50 years or so.

                  I guess not.

                  Maybe one day they will realise changing the body and interiour every year is pointless, and actualy focus some kinda effort on actualy making them.. better..
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                  • #10
                    I have a 94 Ford Aerostar with a 4.0L V6 w/AOD trans. It's the extended version that will carry full sheets of plywood. I've gotten mileage as high as 28mpg on trips and get around 17-20mpg for local driving. They've got to be doing something different. The engine has a lot of guts even in the van. Maybe they can't keep their foot out of it.

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                    • #11
                      Ranger? 15 mpg? it's a LITTLE truck, should be double that.

                      My S10 gets 25+, rated 29/30 by EPA.

                      Now that GM makes no small trucks* I was going to get a Ranger if I have to replace the 2000 S10...... but you just fixed that idea.

                      Asian? Guy at work has a Japanese truck, a hair bigger than the S10. It gets 12 mpg...... he told me that the other day. I'll have to see what brand/model it is.

                      * no acceptable ones.... I hate the Colorado, and so do several people I know who have them.
                      1601

                      Keep eye on ball.
                      Hashim Khan

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                      • #12
                        Originally posted by saltmine
                        At the Proving Ground, one had to open the hood to determine if the powerplant was a side-valve four-cylinder or a SOHC V-6. Of course, the four-cylinder got much better gas mileage.

                        Do Ford still make a side-valve four-cylinder? I though that gave that up after the...

                        ....Ford Anglia 100E!

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                        • #13
                          I hate the Colorado, and so do several people I know who have them.
                          Wait till "saltmine" reads this.

                          You mean to say that not everyone is in love with all that mother GM produces?
                          Is nothing sacred anymore?
                          Home, down in the valley behind the Red Angus
                          Bad Decisions Make Good Stories​

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                          • #14
                            Its funny, I get a consistant 21mpg with this tank, and 14.5mpg pulling all of crap behind it.

                            Andy

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                            • #15
                              Originally posted by Willy
                              Wait till "saltmine" reads this.

                              You mean to say that not everyone is in love with all that mother GM produces?
                              Is nothing sacred anymore?
                              They made the S10 OK, but they lost money on me....... they had to rebuild the tranny once, for $1500 equivalent price and the anti-theft went out so it was cutting off the ignition after 2 sec, that was $700 equivalent.

                              I didn't pay a dime for either fix, so I reckon they lost their shirt on me. I know the parts were low cost for them, but they had to pay labor too.
                              1601

                              Keep eye on ball.
                              Hashim Khan

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