12.75mpg on Ford ranger 4.0L 5spd....

[hermitjohn]

First tank since I bought it gave 16mpg. Second tank 12.75mpg... Yea I dont drive a lot! Ok this is stupid, my old carburetor non-computer F250 4wd gets 12 to 13mpg. In my head this Ranger V6 should get at least 18 to 20mpg. I know i can tune an old non-computer F150 to get that.

Somebody said pull the oxygen sensors. I did today. One had nice light tan colored tip like spark plug in well running engine. The other was carboned up like a plug in an engine running very rich. Looking online, they said its either a dead oxygen sensor or a leaky injector.

Anybody else with a suggestion. Obviously the one bank of cylinders is running pig rich.

[comfortablynumb]

I just put 02 sensors in the old 2000, it boosted the MPG from 15 to 18 on the meter. They should be changed now and then.... they get slow.

[hermitjohn]

This modern (22 year old...LOL) stuff sure isnt cheap to keep. But ok, replace the oxygen sensors, fine. Obvious that carbon covered O2 isnt functioning. Its a high mile used truck, and that usually means its going to need stuff fixed, I knew that when I bought it.

Any idea why they need two oxygen sensors, one for each bank of cylinders? and yes I know the OBD2 has one or two more to make sure the catalytic converter is working.... Lucky I dont have that, especially since I'm pretty sure the catalytic converter is non-functional at 190k. But would seem one 02 would be enough, wonder how the computer would react to one oxygen sensor and second set of leads soldered to the first set.....

[comfortablynumb]

The v6 has 2 banks of 3 cylinders. This is a way to narrow the diagnostics and maximize the efficiency of the engine. If it had one o2 sensor it would correct all 6 instead of just 3.

If it is OBD2 you can plug in a live data scanner and track the long term fuel trims on each bank. If the computer is correcting for a lean or rich condition on one bank to far out of normal range then you can figure out where the problem is.

The LTFT is the baseline correction for the air fuel mix, and it is constantly recalculated by the input of the short term fuel trim data. The computer is constantly at work keeping the fuel mix at 14.7:1 using data from the o2 sensors, the mass air flow sensors the air temp sensor and a bunch of other sensors. If everything is working right, the computer can correct for a rich or lean condition until it gets about 20% out of whack then it throws a rich or lean code on the bank in question.

Thats the drawback with the OBD2 system... if you dont have the data, you end up replacing stuff that compounds the problem.

[comfortablynumb]

I dunno I have found rangers fairly cheap to repair compared to most cars.

[hermitjohn]

Its a 94, not OBD2. I was just reading that the OBD2 Rangers had yet more oxygen sensors after the catalytic converter to determine if the catalytic converter was performing properly. Learning all the extra annoying expensive carp they added to OBD2, pretty sure I dont want one, though never say never, if thats what is available/legal.... then one just has to suffer through it. Sure there were earlier generation people that didnt see a reason to upgrade from the Model T or from the horse and wagon. I am just getting old and dont like change for change sake. But change is coming faster and faster.

I still dont see the problem with computer correcting all six together. I drove vehicles for years with one carburetor servicing four, six or eight cylinders. Even into the computerized fuel injection era, they used to have throttle body injection with one or two injectors basically acting like carburetor used to act, servicing all cylinders. If they had stopped there, think that was genuine improvement, at least over the computer controlled mechanical carburetors, those were a monstrosity. with non-computer carb it can be tuned for mileage or for emissions, rarely both. Thats where computer systems are improvement. They can give a good compromise for both emissions and mileage. But stuff they have now belongs on exotic sports cars and luxury cars for people with deep pockets that trade cars when ashtray is full, the throttle body system was simple and relatively cheap given the need for emission controls. Sure beat all the Rube Goldberg emission controls on 70s era cars if you lived in state with emission inspections and couldnt just remove/disable them.

Modern Rangers are not cheap to keep, compared to older non-emissions, non-computer vehicles with a straight six or straight four engine and manual transmission. But yes, I imagine Rangers are cheap as far as modern era computer vehicles go. They (at least 22 years ago now) had pretty conventional chassis and drivetrain. I even figured out why my Ranger handles so well, they put serious sway bar on both front and rear. Again not cutting edge technology, but effective. Much simpler than the computer controlled "magnetic ride control" stuff I see advertised on tv. I still find it hard to believe people actually truly want more complex vehicles for whatever TINY increment in comfort it might provide. More profitable for the manufacturer no doubt, but not benefit to the consumer interested in cheapest transportation from point A to point B.

And if computer is so efficient why does a Ranger get less fuel mileage than the old 1960 Chevy Apache pickup with similar size engine with crude one barrel carb servicing all six cylinders, and four speed? Heck it didnt even have a PCV valve, though PCV valve actually a very good thing for both emissions and engine longevity. It was full size pickup with 8ft bed. No special tuning and it would get 16mpg. It was geared for work, not mileage and had no overdrive. If I had put say a 3.08 rear axle in it, would hit 20mpg easy. Now tell me again how all these expensive sensors make everything so more efficient on the smaller size Ranger?? Sure if a V6 RAnger got 35mpg, I'd say hallelujah, all the complex expensive technology is probably worth it though still PITA for people stuck with it when it has high miles. Reading online the 4.0L Ranger engine even 2wd and short single cab with 5spd rarely got more than 18 to 20mpg. You read one guy here or there with the SOHC version getting 22 or 23mpg, but even thats rare. We are still talking in range of non-computer carb fuel mileage when they are geared and tuned for gas mileage, nothing a non-computer full size pickup isnt capable of.

[hermitjohn]

I gotta say maybe the thing I like most about this ranger was no rust and no water leaks and no cracks in windshield. Its been rare over the years to find a rust free older pickup. The reason I finally sold the Apache was because it had developed serious cancer around upper part of windshield frame. And the bed was rotted out, just had sheet plywood in there. I frankly hate serious body work. Mechanical, fine, if its not some cramped futzy kind of thing where you need to be double jointed with hands small as a pixie, but dont enjoy body work at all.

My F250 is developing some similar rust problems, so suppose one of these days need to find same era body for it thats solid. There for a while they were really cheap, usually ones with an automatic that quit and werent worth replacement automatic, but I wasnt in good health so didnt want the hassle getting it home, let alone swapping body over to my truck.

Wish I had crystal ball to know whether I am going to have hassles with some national emission inspections in future. That would make restoring an antique body and putting it on modern chassis worth the trouble, even hiring some good body man that works out of his own shop. Shops that do insurance work not worth the trouble. Too expensive and they dont like custom work. Probably though end up being my own body man like I do everything else for myself cause I cant afford "professionals".

[comfortablynumb]

By using the OBD2 and higher data, most of the time there is no tossing parts at a problem to fix it. The data narrows down a problem and makes fixing it easier.

But back then... there was no emissions to deal with.
Our 88 toyota can run just fine with the whole computer unplugged, it just runs a little rich by default but otherwise, no problems. Try unplugging an OBD2 engine and running it. LOL

So I see your point. No emissions regs made the machine less complex. With a more complex emissions system you have to control it with a computer.

[hermitjohn]

That brings up my big bugaboo with arbitrary emission requirements. A V6 Ranger that gets 35mpg would indeed pollute less cause it would be burning significantly less fuel to do the same amount of work. But is anybody seriously trying to tell me a computerized Ranger with a 245 cubic inch engine that gets 16mpg is polluting significantly less than a 1960 Apache with 235 cubic inch engine that gets 16mpg? Really?? The percentages of some components of that pollution expelled might be different, but thats all. You are still using the same amount of fuel to go the same distance. Same amount fuel burned (using same amount of atmospheric oxygen) to do the same amount work, means same amount total combustion product expelled. It isnt somehow magically stored by computer into a secret chamber in an alternate dimension somewhere...

You want to seriously lower pollution, you test for total amounts of pollution expelled over time, not component percentages. Meaning the less fuel burned to accomplish the same goal, the less total pollution expelled. The percentage thing came about because in the 1970s, American car companies were mainly making large heavy cars with large engines and relatively inefficient automatic transmissions. If total pollution was controlled, they basically couldnt sell what they were set up to produce. Big engines expel a lot of total pollution compared to small engines though the percentage of pollution components might be same. So they did the feel good percentage thing for the worst components in that combustion product expelled. I think in 70s, cars polluted more because of these rules.

I had a 71 Buick LeSabra (4000 pound) that got 22mpg on long highway trip with a 350 and a three speed automatic, points and 2bbl carb. No overdrive, no pollution controls or detuning for emissions. It was designed as a comfortable hiway cruiser, got 13mpg in town. 1979 was last year that same Buick 350 engine was sold (back then each GM division had their own different "in house" V8, there wasnt one corporate V8). In similar weight car, this 1979 version engine did well to get 13mpg on long trip and 9mpg in town. Progress?? Less pollution?? It burned nearly twice as much gas to go the same distance as it did in 1971. And yes that Buick engine was exceptional, it had long stroke. It was designed for torque and quiet low rpm hiway cruising, not racing. Most V8s were short stroke, meaning they were more emission control friendly, and detuning them made a less dramatic change in fuel mileage. You dont see long stroke engines in modern world since they still are harder to do emission control.

[hermitjohn]

Ok, first Autozone only has tester for OBD2, 1996 or newer. Sorry Charlie...

Truck drove nicer with the new oxygen sensors, pretty sure I could notice a difference. But I would like to know what other little error codes pop up.

So with fingers crossed, I stopped and topped off tank on way home, even though didnt need gas. 13mpg! Up a quarter of a mile per gallon with the new oxygen sensors. Wow, way I drive, think I could get that in a Chevy half ton with a carburetor 350-V8. And those engines were not known for their superior fuel mileage. Have heck of a lot more power to boot. This engine has to still be running pig rich for some reason. No reason in world this shouldnt be getting 16 to 18mpg minimum.

This has me in quandry. I like how the Ranger drives and handles, no super powerhouse, but enough power for weight of the vehicle. but not sure what to do to get fuel mileage up. I am not a grandpa, but I drive like one! So not my driving technique. This is a manual transmission with new clutch, so not some goofy slipping automatic.

[hermitjohn]

Ok, more reading, strongly suspecting the coolant temp sensor that sends reading back to the computer. There are two, the other just sends signal to the dash temp gauge. The gauge works. The computer's temp sensor can make a huge difference in fuel mileage if its bad. Costs about $16 from RockAuto.com. The temp sensor for computer of course is in a very tight place compared to the one for the dash gauge.

Since auto parts stores want to pretend the OBD1 cars have all disappeared, I ordered an OBD1 for Ford scanner. Cheapest I found was $28 shipped. Didnt want to, but I really hate trying to count blinking lights. Honest would it been so hard for car companies to build in a display for the stored codes? Not sure what genius thought counting blinking lights was way to go. Car companies put lot money into stupid stuff, then neglect important things.

Should wait for the scanner to see the codes. Pretty sure a bad temp sensor would throw a code.

[hermitjohn]

Oh great found another possibility. Seems on first generation Explorers (same mechanicals as Ranger), the fuel pressure regulator was a common problem. It fails and pressure is too high so more fuel than necessary is injected. And yep, around 13mpg instead of 17mpg.

So not only do modern vehicles have zillion extra parts, you also need extra tools to deal with these parts. A fuel pressure tester most likely would be good start. Though one guy said, he measured fuel pressure, it was ok, but still ended up being a fuel pressure regulator...

Ok, guessing now, pure guessing, that probably little more likely to be a fuel pressure regulator, than a temperature sensor. Again wait until I see what codes are stored.

Like I said before, all this complicated nonsense would be justified if dang vehicle got 35mpg when working correctly. But it doesnt get any better mileage than a non-computer carb engine, worse in some cases.

[hermitjohn]

Went out and tracked down the pressure regulator. BINGO. The vacuum line from it to the manifold was missing and both ports capped off. Pretty sure some shade tree found diaphram ruptured and gas being sucked directly into the manifold through vacuum line. When he priced what these little jewels cost, he just capped vacuum ports. This keeps gas from being sucked directly, but it also means no pressure regulator function so injectors getting full fuel pump pressure and thus crappy mileage.

So sure of this, just ordered a new regulator. These buggers are expensive though lot less expensive than back when this vintage Ranger/Explorer was lot more common. Ford combined pressure regulator with fuel pump in the gas tank in late 90s. So one goes bad, you replace both. But reduces demand for the older version I need, so price came down. I ordered cheapest one I found, hoping I didnt make mistake in doing so. It is sold under "Standard" brand name. Lot times better to order the MOtorcraft version of these little bits and pieces.

[comfortablynumb]

Junk yard rangers are full of good parts like that. Find one that will let you pick around. you have a good chance of picking a couple of good ones.

yeah blocked off vac lines will cause you grief, if there was one blocked there is probably several more.

[hermitjohn]

Too bad I dont have a u-pull-it yard nearby, but I dont. Regular yards dont want customers out in yard and you would pay as much as new one to have them remove it. And real gamble on common problem part like this, to buy it used, if you have to give more than couple bucks for it.

[hermitjohn]

FedEx had delivered my code reader to end of driveway without sending notice of it being delivered. Lucky I was headed down to clusterbox for couple small packages that sent delivery confirmation.

So after finally getting it plugged in correctly (it can be plugged in two ways.. the right way and the wrong way) I downloaded the codes:

159-- Mass Air Flow sensor fault

327-- EGR valve circuit below minimum (my year Ranger doesnt have an EGR valve!!!)

522-- Vehicle not in Park or Neutral while doing test

341-- Octane adjust service pin open

565-- Canister Purge solenoid circuit fault

558-- EGR valve regulator solenoid circuit fault (again this year RAnger doesnt have an EGR valve)

Now be interesting to see if any of that goes away when I replace and hook up the fuel pressure regulator. It isnt hooked up now due to actions of some former owner. Some previous owner unhooked it and plugged the vacuum nipples. I would assume because the diaphram ruptured in the regulator so raw gas being drawn into the manifold.

I am betting Mass Air Flow sensor error is because I have yet to install the new intake manifold gasket. So reading is outside the expected. I did finally get one. It however is a big job and havent wanted to tackle it just yet since truck runs ok without doing it right now.

Also Ranger is becoming more difficult to start hot. That definitely could be and probably is related to non-functional fuel pressure regulator.

I have no idea what an octane adjust service pin is...

[hermitjohn]

Got the pressure regulator today. When truck cooled off after trip to clusterbox, I installed it. Stole a vacuum line from my old Ranger. It runs, all I know. One trip off the mountain in a day is enough, have to wait to test whether it helps gas mileage for another day.

Went out this afternoon and front tire is flat... didnt make my day! Hoping its a nail and not sharp rock slicing into the sidewall.

[hermitjohn]

I had to go to clusterbox for a package and to mail off my electric bill, so took it out on hiway. Not lot difference in how it drove on hiway. Though I noticed some subtleties. It had bit more power in places and little less in others. It lugged a little better coming up county road big hill in second gear than before. Thats a really good sign. No temptation to downshift to first. I suspect it will at least get back to 16mpg but time will tell.

[hermitjohn]

Ok, got gas today. 10mpg!!!!!!!! Yea, bummer. So still can try the coolant sensor that tells computer how hot engine is. Computer may think engine is perpetually cold. After that I am really out of ideas. Seriously I could put a 460 V8 in there and probably get 10mpg.

For what its worth, it does drive the best it has since I have gotten it. Plenty power, no hesitations, if it had shown getting 20mpg, I would have believed it. And despite the horrible fuel mileage, black smoke is not pouring out the tailpipe.

[hermitjohn]

I am thinking back to when I replaced the oxygen sensors. That one on passenger side was fluffy black. I guessed faulty sensor. But could be sticky/leaky injector. Need to check that out.

I gotta say this is getting to not be much fun. Too many variables. And too little reward if I do finally figure it out. Too many things to throw money at. And if this thing was in perfect condition, its still going to at best get into high teens. There are people claiming miracles, but most people get mid to high teens for mileage with this engine. The SOHC 4.0L version gets a little better, maybe very low 20s. This is doable with a much simpler carb engine.

I just hate giving up on it cause it does run pretty good and has enough power. No doubt has lot miles left in it. But a 10mpg V6 is pushing the limit far as livability. 10mpg be lot more acceptable in a hotrod car, or a heavy duty truck. Something where you figure the low mileage gets something in return. This is not the case with a compact grocery getter truck. Only real advantage it has is the high ground clearance so I can get up and down my driveway without ripping bottom out of it on ruts and rocks.

[hermitjohn]

Ok, took out all six spark plugs. Evil engineers didnt make this particularly easy though I have seen worse. All looked normal light tan like they should. If one injector had went wacky, at least plug in that cylinder should be black. Also it runs fine with enough power, no acting like its running on 5 cylinder or anything. No pouring out black smoke.

Well looks like that temperature sensor is my last hope and pretty hard for me to believe that alone would cause such poor mileage. I can test resistance of all injectors, but only three are "easy" to get to. Others require some disassembly.

[hermitjohn]

Been thinking about it. I believe the computer is in some limp home mode for whatever reason and not advancing the ignition timing for best fuel economy. I know back in days of carburetor cars, if diaphram in vacuum advance on distributor ruptured, you still got enough mechanical advance to keep vehicle drivable, but fuel economy tanked. Very similar to what I am dealing with. Its not running pig rich, but it is getting very poor fuel economy. Ignition timing not properly advancing could do this.

Now with one of these EPA computer cars, there is no easy way to test ignition advance, nor to directly correct it if that is problem. Engines dont have distributors anymore, its all black box mystery theater. You have to second guess the ecu and find out why it thinks it cant advance ignition timing, this wont necessarily throw a code. For example if temp sensor tells ecu that its constantly cold engine. hoping if you guess correctly, fuel mileage returns. Since the rules the ecu uses to calculate things are some proprietary secret, this can become a complete guessing game.

Wonderful if you are a control freak like EPA and want to keep consumer from making any changes other than throwing new OEM parts at it, not wonderful if you are the consumer and have to correct the problem or else waste a third of fuel you buy. Unfortunately its cheaper to throw lot new parts at problem than to hire somebody that can actually diagnose the actual cause.

I think if my last hail mary attempt to fix with new temp sensor fails, then its going to be that wiring to one or more of sensors is bad.

[hermitjohn]

Update. Somebody elsewhere suggested the incoming air temp sensor would greatly affect fuel mileage. So I pulled it to have a look at it. Its screwed into intake manifold next to the vacuum octopus fitting. It was wet with gasoline. Only way gasoline can get into the upper intake plenum is through vacuum line from the FPR. So that new FPR was a dud though I swear it seems to hold vacuum when I test it off the car. What I get for buying anything but Motorcraft parts. To many cheap imitation parts without much quality control. So one last hurrah trying to get mileage up to something reasonable, will replace the coolant temp sensor, the air temp sensor, and yet another FPR. The temp sensors are cheap, the Motorcraft FPR is not. There are some adjustable universal FPR from China that are cheap, and at least some of them work fairly well from reading reviews on Amazon, but take some adapting to get it hooked into the fuel rail. They are intended for hotrodders that do something silly like oversize injectors, then need higher pressure fuel pump to get enough flow and bigger fuel pump needs bigger regulator and maybe more pressure.... If I keep having problems with expensive OEM style FPR's going to have to spend time adapting one of those universal ones.

[hermitjohn]

Ok, new FPR (motorcraft this time), new coolant temp sensor, and new air temp sensor. Long trip. Drove nice to my destination, even lugged up steep hill in fourth without protest. On way back home felt like I was dragging a boat anchor. Went on past my road to small town and filled up gas. 14mpg. Hey it beats 10mpg, but we are still talking mileage like full size pickup with a V8.

I will putter some more with it, though dont have high hopes of improving it much. At least its not a daily driver or anything. And I like way truck drives/handles so eventually put simpler carb engine that will bolt up to a granny four speed into it. I know old carburetor six cylinder will get at least 18 to 20mpg. Nice living in state without emissions inspection....

[hermitjohn]

Anyway, I finally scraped bit insulation off wires to MAF sensor and ran the test on it. easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/maf-sensor-tests-1 Very steady readings that escalated with rpm and came down again as rpm came down. And the grounds were grounded and the 12V was 12V. So it not only looked new and spotless, but is apparently functioning fine.

I undid my IAC modification and am now getting the hot idle stall soon as engine gets warmed up. Computer apparently didnt like my workaround though workaround kept idle steady. So if I can find spare choke cable, will set it up so I can manually keep throttle open enough so it doesnt stall for another mileage test when I go shopping next week. I am not going to deal with stalling every stop light and every ten foot when looking for parking space so if I have to physically keep throttle open enough for 1500rpm hot idle, so be it. I want to see if mileage goes back to at least 16mpg on regular basis, before putting one more cent into this engine. If it can do at least 16mpg, then will invest in a new IAC since that is only doohicky that hasnt been either tested or replaced. More expensive and needless bit of garbage, cant imagine, but if I do workaround to manually control idle, computer gets in tizzy and apparently runs richer mixture. It shouldnt matter as long as its all metered air going past MAF, but apparently it does.

14mpg is just not acceptable in compact truck with manual transmission and economy rear axle. 16mpg is just barely acceptable and only cause I know this thing weighs an unbelievable 4000 pound. Its a heavy chevy.... errr... Ford. Though I have in past gotten 16mpg in a much heavier 2wd 3/4ton with big carburetor V8, lower gears in rear axle, and 3spd automatic transmission, so still super annoying. A Ranger with manual transmission driven like I drive and economy rear axle, just shouldnt get less than 20mpg unless towing or something else out of ordinary.

[hermitjohn]

I found my stash of assorted o-rings. So could replace bad one on fuel pressure gauge adapter hose. Actually had to use two to make it stop leaking.

But anyway:

So I tested fuel pump. Engine off, ignition on, supposed to be 35 to 40psi. Engine idling, supposed to be 40 or at least 35, bare minimum.

Engine off, ignition on, mine is 35. Ok so far.

Engine idling, mine is 25. Not good. Means it cant supply volume needed at pressure required. Looking online they said 25psi is pretty much lowest pressure that engine can run. This is reason Ranger felt really doggy on way home, like it had the boat anchor deployed.

So guess who gets to change out a fuel pump? Oh boy, can hardly wait....

Believe it or not you can get a cheapie fuel pump for this Ranger for $12 shipped. Noname china version. Now you know that has to be top quality.... NOT. Yea, maybe not want to get too cheap on this. Name brand pumps start around $50. As much hassle as this is, think better to go with a name brand pump. Unfortunately the Motorcraft pump is sold as complete assembly for mere $200, so think I will stick with an aftermarket name brand pump. Bosch or Airtex or Carter or Walbro or such.

[hermitjohn]

Ok, seems Bosch is the aftermarket fuel pump most liked for Ranger/Explorer, so thats what I ordered. Airtex seems to be one to be avoided and Precise seems to be a relabeled Airtex.

I still think its really stupid that car manufacturers dont have an access panel to get to the fuel pump without dropping tank or lifting the box bed. They can spend money on the stupidest knick knacks and decorations to attract buyers, but some low buck super practical thing like this, they avoid.

[hermitjohn]

Found this: www.ford-trucks.com/forums/1102626-tech-tip-1994-ranger-fuel-pump-install.html

That is clever, fairly fast and easy, and better than cutting access panel into the bed. I had seen people lift bed from front like dump truck, but never from side. This is way to do it. Dang, I have cheap set torx bit sockets someplace. No idea anymore where they are. Usually just use small set that are angled like old allen wrenches since usually just need to remove small torx bolts/screws. But guessing the truck bed bolts wont be that cooperative. I remember long ago helping friend get bed off an old Ford 3/4 ton and couple of those bolts werent coming out for love nor money with torx bit, and holes in them rounded. I ended up welding big hex nut to top so could use a big breaker bar socket wrench. That worked, then after installing replacement bed, just ground the nut off. Hoping not to have to do that. That is neither quick nor easy.

[comfortablynumb]

Cutting an access port in the bed floor is probably a good long term idea.

[hermitjohn]

If it was a SUV or minivan, I would cut hole in floor and screw on a sheetmetal patch. But in a pickup with a short bed, seriously if you can loosen the six bolts (hmmm is it four or six bolts???) holding the bed, jacking it up from drivers side, like that link I gave, is better than hole in bed floor. Dont have to disconnect anything except the fender reinforcement rods and thats just couple tiny bolts.

Any access hole unless really beefed up is always going to be a weak spot and nuisance in a truck bed when you haul something. I had a '72 Ford Courier that had a factory access panel in truck bed. It was only useful if you needed access to the fuel gauge float or the sock filter in the tank. So really odd they put it there. Back then engines had mechanical fuel pumps on the engine. But dang if everything didnt catch on that access panel, real nuisance. And yes it could be engineered smooth and strong as rest of bed floor, but that requires more than scrap of sheet metal and some screws.