Fuel mileage: very specific!

[Houston at NCSU]

I have a 94, 4.0L with 3.73 gears. I usually get around 20-21 on a flat highway using cruise, and around 14-16 in town. However, i just put in a K&N tonight, and drilled out my air box, so we will see what this next tank brings.

 

[Haxaw]

96 V8 AWD MPG

Wow I feel really bad for all of the people that have V6's and are getting less MPG than me. I get between 13 and 14 MPG and get around 170 miles to a half tank. I know I have the larger tank. I usually use Regular gas. The computer says I get around 13.5 city and closer to 20 highway. If you keep your foot out of it it makes a difference. I got mid 14's when I first got it now I get mid 13's. Mine is nearly stock but i was wondering if mods would get better MPG like K&N, flowmasters, maybe a different MAS. I heard Pro-M makes a good one but it for horses not MPGs.

 

[Rhett]

12/17 mpg is this ok for my setup

I see this thread and I feel it's time for me to really tackle the mileage thing. I don't think I get the mileage the rest of you with similar vehicles report. Are you living in flat places?

I get 12 mpg 100% in town with my 94 Sport 4x4 (V6 OHV of course). P235 A/T's at 30 psi, 3.27 gears, new plugs+wires, synthetic oil, clean MAF and K&N drop in. It's a hilly place with lots of stop n' go. Highway mileage is 17 mpg.

How do you know if your O2s are bad if your check engine light never goes on? How do you know if you are running rich or not? I don't know what the exh. should smell like if it's rich.

How do you know if your FPR is bad? Buy a fuel pressure tester and put it on the test port?

I don't know if the FPR has ever been replaced, as I bought it a year ago from the original owner, and did not know to ask at the time. He took good care of it, so maybe he took it in to Ford for the 60000 mile service and they replaced it. But I am not sure if replacing the FPR is a standard tune-up thing Ford does or not. I figure the O2's are a standard tune-up thing that Ford does (they should be, anyway) but again I don't know if they are original O2's or not. If they are, they've got 80000 miles on them and are probably ripe. Thing is if the FPR is worn out then it will foul new O2s.

 

[MOTO MIKE]

Hold on a sec.

Ok, I'm a little confused. You say if the FPR is weak, it causes MORE fuel to enter the injectors and wastes fuel. I don't think I understand that. the regulator is on the wrong end of the fuel flow for that to happen. or is it. My manual shows the FPR to be at the end of the fuel flow, meaning that if it got weak, the fuel pressure would DROP. That would mean LESS fuel entering the injectors, and less power. Now with that in mind, how could the FPR cause a bad mpg problem? would lower pressure in the fuel manifold cause bad mpg?? I would think it would cause it not to run, or run badly. Am i chasing my tail looking for the answer in the FPR?? could it be another component I haven't seen yet?

 

[MOTO MIKE]

Rhett, as far as o2 sensors go, when in doubt, change 'em out.

 

[Rhett]

As I understand it, the FPR can cause bad mileage because if it's "weak" as you put it, the FPR can allow too much fuel thru and into the engine. Thus the rich condition. Really I think the term "stuck" applies to an FPR's internal workings since it meters the fuel to the engine, and if this metering mechanism (probably a metal flap) becomes stuck, then too much fuel enters the engine.

..and if it's running rich, that rich condition in the exhaust can destroy your brand-new O2 sensor(s). That's why I am trying to determine if the FPR on my Explorer is ok or not. Then I will change the O2s. O2's are too expensive ($44 a piece, and my 94 has 2 of them) for me to just casually change them without knowing the real cause of the problem.

I'll probably just buy a fuel pressure gauge and be done with it...

 

[MOTO MIKE]

you should feel lucky, my o2 sensors cost $130.00 a piece. I guess there are at least 6 different types on the 94 explorers, just my luck to get the expensive ones.

 

[Tony91Sport]

Im getting 19.5 after I figure it out, im not sure what im getting city/highway. Ive got a 91 and my car spark knocks real bad. Could this be that there is too much fuel in the combustion chamber? Ive never replaced the FPR, and ive had it since 93. Is there a way to test it with a multimeter or something?

Tony
91 Sport 2WD

 

[93 & 96 EB & XLT]

Hey. On my 93 xlt, im getting about 12 mpg with mostly town driving, with a quite heavy foot. I was getting about 6 or 7 mpg, but then I got my FPR (new one) and so its better now. I have replaced the thermostat and the sending unit. Is there anything else that could be getting me bad milage, or is this pretty normal now.

 

[Dennis Brown]

FPR

Hate to show my ignorance but what is a FPR? Fuel pressure regulator? I have always had poor milage in the city but for the past year or so it seems to be worsening to 12-13 MPG. I don't think the Ox sensor has ever been replaced though.

 

[npearman]

Mileage

I have the exact same truck as you. 94 4door 4x4 with the same tires and gears. I get somewhere in the neighborhood of 13-15 mpg. I filled up this morning with 256 miles shown on the odometer and it took 17 gallons of gas. This was combined highway and city.

NP

 

[Haxaw]

Milage huh

I get:
11 mpg in the snow.
13-14 city
16-17 highway at 75 MPH, I'd probably do better if I slowed down.
It's definately a bear though it will pull and go through just about anything.
24+ inches of snow in the drive way no problem i even got through a five foot snow bank at the end of the Driveway, 8-12 more to come Friday.