I have just ordered (finally) a new computer for my truck (99 Ranger 3.0 V6 ) and will hopefully install it by the end of the week. Waiting till then to run odb scan.. I am getting terrible gas mileage ,,, what parts besides plugs and wires of course would help with gas mileage????? Truck came with new EGR valve,,, should I put on new oxygen sensors ,,,maf or map and what about the idle air,,,,,,,did i miss any,,,,, throttle position ?????????

 

ok no comments,,,,let me try again,,,,, what parts can cause bad gas mileage besides spark plugs and wires ????????????????????

 

Weight is the biggest cause of gas consumption, the heavier the vehicle the greater amount of energy required to move it, think motorcycle versus SUV.
Then if you reduce the weight, by removing heavy items, like the spare tire, or the passenger seat, or the bed, you will get better gas mileage.


If you have the flex-fuel version of the 1999 3.0L then there is a unit in the fuel line that analyzes the ethanol in the fuel and informs the computer so that the combustion process can be modified as appropriate. This unit might be bad.


Tell us more about your truck, is it a long bed? 4wd? extended cab? all those would increase gas consumption
I get a solid 21 mpg in my 1999 3.0 L flexfuel extended cab standard bed, no spare.

 

A couple of months ago, I took a 1,000 mile trip with my wife in our '98 Ranger 3.0/manual-trannied truck that has a 7-foot bed. We got 28 mpg with it. This is with me driving somewhat sensible and my wife usually driving over the 75 mph speed limit.
Start with the simple things, like Motorcraft or Autolite spark plugs, a new air and fuel filter, tires properly inflated and then check the more complex items, like codes that may not trip the CEL, or a thermostat that is not up to temperature. I feel that 5W-XX oil is important.
Keep detailed notes of mpg for each tank of gas and perhaps even try a different brand of gas at each fill up. See if your mileage improves any measurable amount by avoiding jackrabbit starts. What rear end ratio does your truck have?

 

ok here is a little more info on my truck ,,,1999 3.0 v6 flex fuel ,,, new egr valve was on when i got truck,,,extended cab,,,, have new computer ordered,, put new fuel filter on already,,, and camshaft scynronizer and position sensor,,, all tires are inflated proper and i dont think it is getting 10 miles a gallon ,,, would bad oxygen sensor cause bad mileage????????? oh and it is 2 wheel drive !! at g k50 i saw that unit in fuel line while i was changing the filter and wondered what it was,,, thanks for the heads up !!!

 

^+2 on the above ideas in trouble shooting mpg problems.
I agree that with between 125-150k miles, the up stream O2 sensors likely belong on your suspect list.
If you have trouble codes, post up All code Number clues you have, or can come by & resist throwing parts at the problem until you get the scheduled maintenance replacement items in place & scan the computer again for any trouble code clues. Let the code clues guide your mpg trouble shoot. We're to work & put right the lowest trouble code numbers first.
Good idea to begin bringing All due past & present scheduled maintenance replacement items up to date. With the mileage on this puppy don't forget the PCV valve as its due for replacement. As its down stream of the MAF sensor & thus not monitored by it, any plumbing vacuum leaks to it, or other acting out of the PCV valve, like sticking open, or not closing, or not sealing well from worn seats, or a weak/worn spring causing it to not act right inside, can cause it to corrupt fuel trim & muck up mpg & performance.
Why was the EGR valve replaced, they rarely go bad, unless rusted & falling apart.
What's caused you to come to believe you need to replace the computer???
More thoughts for consideration, keep us posted on your trouble shoot.

 

oh i know the computer was bad,,,, had starting problem and truck would not start till sprayed with starting fluid ,, i put on used mismatched computer off a 95 ranger with v6 till i could get the one i ordered ,,,, gas mileage was bad with original computer also but at least it starts now without spraying,,,original computer was not telling injectors to spray ,,,, i only drive it rarely till i get the new computer,,, i got this truck used so no idea why new EGR ,, will change pcv and check all the vacuums next after i install new computer then run odb scan ,,, thanks this was very helpfull info ,,,, oh got the new computer thru flagship one for $138.76 with lifetime warranty which was lots cheaper than anywhere else,,, and they update and program it by last 8 vin numbers ,, so it should be a good one i hope

 

Just throwing this out there because this will drop you mileage drastically.
The sliders on the front brakes get stuck and the brake calipers don['t release and the brake pads drag too much on the rotor. Verify your sliders are working. The sliders require maintenance or they get rusty.
My truck dropped to less then 10 miles/gallon when my got stuck.

 

Thanks for the heads up Green ,,, i will check them over but i really think they are fine,,, I have on several times coasted for a ways before turning into my drive and did not feel any drag or here any brake squeeks

 

Was the mismatched computer from a "flex fuel" Ranger???? If not, the fuel injector squirt time programming calibration will be off, as the flex fuel engine has to use a different fuel injector to keep the air/fuel ratio in trim, if the sensor detects a higher % ethanol/O2 content fuel is being used. So using a non flex fuel programmed computer won't properly drive/squirt the flex fuel injectors, thus no surprise the mpg is mucked up.

 

curious, you say you swapped in computers, but did you run into any problems with the pats system? My understanding is that the computer is what "codes" the keys to the truck. So new computer would be looking for keys from the truck it came out of.

 

Correct me if I'm wrong, but wouldn't that be only if the truck has the PATS? My '98 is a stripper and doesn't have PATS.

 

Yes, I was refering to the pats system. The OP would have had it in his truck. I cant speak to your year and modifications.

 

PawPaw I am not sure if the mismatch computer came off a fuel flex but i can find out,,,,,but your explanation makes a lot of sense,,,, and to mfp4073 i think my truck has the pats system on it,,my theft light blinks while driving down the road,,, but no starting issues,,,, go figure,,,the theft light should go off after truck starts ,,, hope new computer does not give me a pats problem,,,should be here in a few days

 

Well I finally got my computer in and installed it and crossed my fingers on the possible PATS ( passive anti theft system ) issues. Just my luck truck would turn over fine but not start. So i called local ford dealership and took the the truck today using the mismatch used computer. Told them it was a PATS issue THEY said it would be fine after a relearn with their scan tool or whatever they use. After 3 hours of waiting they return the truck to me with the used mismatch computer back on it. Told me it had a PATS problem and I all ready new that. Then they presented me with a bill for $237.33 and told me for another $200.00 they might be able to tell me whats wrong with it ,,,, what a rip off ,,, I am so mad right now I could eat horseshoes and spit nails !!!!!!!!!!!!!!! Oh they did sell me one chipped key it was $39.95 so I guess I was charged about $190.00 to be told it was a PATS problem and I told them it was a PATS problem when I took it there aaaaarrrrrggggggg !!!!!!! Now they say either the new PCM is bad or bad transponder or bad PATS module ,,, thats the reason i took it to them in the first place,,, now I am out $237.33 and back where I started.