I have a 2003 supercab 4 door 4.0L 4x4 ranger XLT automatic
my fuel mileage has been almost outragously low and i have done everything i can think of to try and fix it, fuel filter, spark plugs, wires, air cleaner, and even the seafoam thing, I also cleaned but then ultimately replaced the MAF. Before each replacement i always unhook the battery due to possible clumsyness, and each time my fuel mileage doubled but for only about a week. I usually run about 60-70 miles a week. I am getting 8-10mpg and each fix usually put me back around 16-18. So after months of stress and talking to several ford dealerships, which were no help. I decided to just unhook the battery and thats all, well after that It put me back up to the better fuel mileage! So im guessing the computer is running me a very rich fuel mix which i assume will destroy my cat converters very soon along with unaffordable mpg. can anybody suggest any fixes for this? Also no codes are being thrown, ive checked with a scanner. and it runs good no hesitation, good power. I also replaced both upstream O2 sensors.

 

It's possibly the EEC, but more likely one or more of the sensors is not reading properly. When you pull the battery, the EEC will reset to some default set of values for fuel and spark. As it runs the engine, it is re-learning based on what it thinks the engine is doing. The fact that it keeps doing this every time you reset it indicates that the EEC itself is running properly, but it's getting some readings that it's trying to adapt to that results in really bad gas mileage. It could be running way too rich and not realizing it, like the O2 sensors are not working properly, or retarding the timing based on some other readings, such as coolant or air temp sensors.

Did you run a self-test on the EEC to see if it shows any error codes? You can usually go to a local auto parts store and have the codes read for free.

 

yes i have ran a self test but i do have a pretty cheap scanner $40, i don't know if that will make a difference, but no codes are being thrown and i have already replaced both the upstream O2 sensors and the MAF. The engine temp gauge does seem to work pretty good i can watch it warm up slowly with time and if i turn the heat on it even starts to drop a little before climing again the response time is good i guess is what i mean. It runs the same temp as i can always remember when heated. What other sensors could be affecting this issue?

 

The EEC uses a different set of temp sensors than the one used for the temp gauge. So you can see the temperature change on the gauge, but that may have little to do with what the EEC is sensing. Having said that, I think the failure rates of those sensors are very low.

Your cheap code reader will probably show you any error codes there are to see. But too often, the engine performance has to go way off before the EEC throws a code. You can test it by injecting an error condition, like unplugging the MAF sensor, and see what it reports.

If you can check timing, see what it is right after you connect the battery, and then again a week later, when the mileage drops. Without more sophisticated instrument, you can't check A/F mixture.

Let me also say that I am guessing, based on your descriptions, as it is kind of puzzling.

 

well i searched through the tech info page and could not find a link for how to check the timing, soooo... how do i check the timing

 

someone told me to get a vacuum gauge and test the engine with that, has anyone had any experience or opinions on this method whether it would work for my issues?

 

The engine uses a distributorless ignition system, so you can't set the timing, but you have to trust the EEC to do it. So I'm not sure if Ford provided the standard timing marks that allows you to check the timing. Therefore, you will have to check timing differences between the times that the engine gives good mileage vs bad. Hook up a timing light to one of the spark plugs and fire through a gap in the front dress that allows you to see the harmonic damper. Make some reference mark that you can compare to after the EEC has retuned itself, and see if it's significantly retarded.

Also, make sure that the "octane shorting bar" is installed. It is sort of a switch that set the base timing for regular gasoline. Some times people using really bad gasoline causes the engine to knock, and one fix is to remove the bar, which retard the timing a few degrees. It's a little gray 2-prong plug hanging loose from a harness, usually at the rear of the hood at the driver's side. You may need to check a service manual for you truck to find it.

A vacuum gauge is still a very good diagnostic tool even on most of today's gasoline engines, if you know how to read it. Most engine service manuals should have a guide.

 

Ok, ill be picking up a service manual real soon. I've never heard of a octane shorting bar ill definitely be looking for that. Ill have to wait till this weekend to check the timing.
Thanks for all your suggestions!

 

ok i got a service manual and for the life of me i cannot find the "octane shorting bar" anywhere under the hood or in the manual. but good news i was talking to a machanic at the ford shop i bought it at and he gauranteed me that nothing is wrong with the comp. and if their was it would be because the previous owner programed it with a tuner but he insisted that every used vehicles comp. is checked before it is sold. Now i doubt this very much myself but i wipped out my scanner while on the phone with him and went over the fuel trims and whatnot and he agreed the readings were not normal. He seemed to imply that i was good for a free reprogram but told me he would call me back after talking to the manager. Somehow i doubt that it will be free but maybe a discounted price would be in order. we'll see what his callback will do

 

That was a custom programmed EEC? Then just about anything is possible. I hope they can fix it for you. Maybe the best thing to do is have it re-programmed to stock settings.

 

yeah, i plan to. hopefully its on the cheap also. I just can't imagine that there was enough gain in power to justify that kind of fuel economy. My '96 ranger 4x4 4.0 super pulled very similar but i had an exhaust, intake and ignition on it but i was getting 18mpg and over. LOL maybe thats why the guy traded it in

 

After reading your post I just had to chime in. Bartkowski I have a 03 Ranger 4.0 stick that I bought used a year ago. 73,000 miles. I was having some of the same issues that you have. Bad gas milage, Idle that surges between gears, Intermittant hicupping at hyway speed. I like you replaced plugs fuel filter etc. and could not get it to run right. So after much deliberation I took it to Ford dealer here and described my symtoms and asked them to check for any codes, etc. Well now my truck is a whole different machine that runs perfect, smooth and way better MPG. What they did was reflash PCM, recalibrate to latest levels, perform gas injector flush and intake cleaner. I don't know if the flush is a ripoff, but I don't care as now my truck is the way its supposed to be and I am thrilled to have the driveability that it was made for. Good luck with yours.

 

hey gearheadjo, how much did all that cost you? i haven't had a chance to get mine in yet, im in the middle of a move to a new place and between the cost of sec deposit and now gas i didn't want to chance having to try and move with out it.

 

The reflash was $102 and the flush was $232. All I know is my truck runs great! Good Luck with yours.

 

thanks gearheadjo, its nice to know that someone has had the same problems i am having.