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Really Bad Gas Mileage

Smaug

Member
Joined
February 2, 2008
Messages
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City, State
Upstate Western New York
Year, Model & Trim Level
1991 Explorer XLT 4x4
I'm only getting 10 mpg (4.0L V6 Push-rod Engine, OD Transmission). When I start up no smoke from exhaust for 30 sec then white smoke that smells like raw gas, no back fires or obvious miss-fires. I am planning to do plugs, wires and air filter ASAP.

(4.0L V6 Push-rod Engine. OD Transmission)

What ideas do you all have as to what else may be wrong?
 



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if i were to guess ....could be few things ,needs a tune up ,possible head gasket issue (dont quote me tho) or the fpr has gone out (fuel pressure regulator) .....but you smelled gas real bad right ?? then try looking into the fpr that could be faulty and that could be your problem .

also do you have oil and water mixed in the crank case or radiator? if yes then def a head gasket problem .


hope this helps . . . . :salute:
 






I would definately do the air filter, plugs, wires and maybe even the fuel filter. I was pulling about 14 city MPG and like 2 ponies, until i replaced them, now im back at full power and about 17-18 city MPG. Mine too smelled like gas, incomplete combustion and the engine was jerking...
 






Reply To; boggs1227

if i were to guess ....could be few things ,needs a tune up, possible head gasket issue (dont quote me tho) = hope not head ache.:(

or the fpr has gone out (fuel pressure regulator) .....but you smelled gas real bad right ?? then try looking into the fpr that could be faulty and that could be your problem. = Worse when air and engine are cold.:confused:

also do you have oil and water mixed in the crank case or radiator? if yes then def a head gasket problem. = Doesn't seem to be; Coolant looks OK. Don't smell gas on the dip stick.:cool:
 






to: ParkerRocker

how are your plugs? Don't know yet.:confused:

I was pulling about 14 city MPG and like 2 ponies, until i replaced them, now im back at full power and about 17-18 city MPG. Mine too smelled like gas, incomplete combustion and the engine was jerking...

According to Ford the city MPG rating is only 14MPG for my engine but 14mpg is still better than 10mpg. Engine not jerking. I hope it's just plugs, wires, and air filter.:confused::confused:
 






check your cat . if its pluging up it will effect your gas milage. free flowing exaust is very important any obstructions and you will lose horse power ,gas milage. you said you smell raw gas that says tun up but the problem may have spread to the cat now . to much gas in the exaust will seriously hoop you cat and cause it to get plugged good luck buddy :thumbsup::roll::salute:
 






Check the FPR

When mine did this it was the fuel pressure regulator. I pulled the vaccume line from the fpr and a bunch of gas pored out (good thing the engine was cold).
 






I Have replaced the air filter, the plugs and wires as well as did a compression check which gave me a reading of 180 lbs. @ each cylinder @ 10 (?) sec. Which should rule out head leak??? and valve leak??? RIGHT???? MPG situation doesn't change when the engine is warm. On a cold day I can use about 1/4 in about 50 or less. I can some times smell raw gas outside the truck when I get out but no obvious leaks.

What about the Mass Air Flow sensor????

What if the pre-heater hose is leaking and feeding cold air all the time?

What about charcoal canister flooding?

No fluids cross mixing... Oil's Brownish... Trany's Redish... Radiator's Greenish...
 






Pull codes! The pre heater tube wont make hardly any difference. "White smoke" is probably just normal steam, pretty much all cars do it a bit after they start. Are you actually measuring your gas mileage or guessing based off of your gas gauge/odometer?
 






I'm calculating my MPG.... Miles/divided by/gallons=MPG.

Now I know that both my odometer and speedo reading and my MPG will be effected by my 1" taller than standard tires. BUT it should be a constant/fixed change and not fluctuate simply due to outside temperature changes. But both my speedo* and my MPG do fluctuate solely due to temperature changes.

I've never owned a vehicle whose MPG got worse as the temperature changed. For instance my car gets 27 MPG City all the time.

Yet to check my FPR and Cat, but wouldn't the MPG just suck all the time.

If it was the old carb and mechanical/vacuum choke setup I'd just reset or change the choke coil and make sure the vacuum line was connected.

Oh yeah the engine runs just fine other than sucking gas when it's cold.

*See my other post regarding my Speedo issue.
 






Everybody has great ideas.. but i didnt see anything about oxygen sensors. a bad one can cause the truck to run too rich or too lean.
 






But an O2 sensor should trigger the "Check Engine" light (which works) but it's not on.

Once again both the Bad MPG & the Speedo reading fast (see "Bad Speedometer/Odometer Readings" post) are affected by cold (below 50-60 deg F) outside temperatures. 65 deg F and above MPG is 13-14 City & Speedo gets increasingly more accurate. Oh yeah, I drive about 75% city and 25% highway]....( factory original is 14 MPG City )

By the way, where is the connector for the code reader located?

I really appreciate the help so far.
 






On a pre-OBD II vehicle (pre '96 or 95, depending on make), a bad oxygen sensor won't necessarily trigger the Check Engine light. One symptom of a bad oxygen sensor is an unsteady idle, but that can be caused by many things.

You can find online calculators that allow you to correct for oversize tires in your gas mileage calculations.

FWIW - I replaced the plugs in my '92 4.0 Explorer and the gap was .105 - huge. Factory spec. is .52-.55. The mileage so far has gone up .3 mpg/gal. - so no big deal there.
 






OK, I'll bite what's "OBD II"?

Other than crappy cold mileage the engine runs fine, smooth through the whole acceleration range, quick off the line, no stalls, and in cruise shows no abnormalities.

Tach shows no bounce or flutter

I used high end 4 prong platinum plugs. No noticeable MPG increase but way quicker starts.
 






Get codes pulled.

When you have that done, check them in my thread:
http://explorerforum.com/forums/showthread.php?t=227663

Make sure to check with key on engine off, and also key on engine on.

Doing that might give some indication as to what needs fixing.

You have a few locations to pull codes, there's a test port on the driver side where you use a voltmeter or test light, and then on the passenger side there's a EEC-IV connector.

If you go to Autozone, Advance Auto, or any place like that, they SHOULD be able to pull codes for you FOR FREE.
 






OBDII is 'On-Board Diagnostics II' - a federally mandated set of engine codes (from 0000-9999) that are required on all cars and light trucks sold in the US since 1995. Some manufacturers went to it slightly sooner than others. All vehicles with this certification must have a sticker under the hood saying so. There must also be a diagnostic connector within 20" of the steering column (for inside use) and usually there's one under the hood.

More at: http://en.wikipedia.org/wiki/On-board_diagnostics

While OBDII, in my experience, can generate more trouble codes than you'd like to see, you also stand a better chance of being able to figure out what's wrong. When I get an OBD code (such as P0420), I just put the code into a search engine and see what the rest of the world did when they got that code.
 






I too am having the same problem with the raw gas smell. The truck runs fine and has had a recent tune up (plugs wires etc.) The truck is stock except for the dynomax exhaust, I smell the gas after I get out of the truck right around the left rear quarter, could the fuel pump assembly be rusted out and leaking? I had to replace the whole fuel pump assembly due to the rust problem on my '92 but I attributed that to the fact the whole darned truck was rusted out (came from michigan the land of road salt :eek:) but is that a common problem for the x's?
 






left side huh? i would take off the rear drivers wheel ( to get better access) and see if the locking ring on the tank is not rusted out and also inspect the filler hose that runs to the tank from the filler door ....i have seen those rot out if all are ok then look to the engine for problems.
 






just wondering if anyone has experienced bad fuel mileage and replaced the 02 sensor and found the problem fixed?

my 92 is still running decent surprisingly, i used to be able to get on an average of 18 but now more around 13/14 area, i know its old, but it still runs strong, and i know 02 sensors only last a certain time.

was wondering if it would be worthwhile to just go ahead and change it.
 



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your right with age every thing part wise dies eventually .one time i was at advance auto i asked if they hada cleaner for o2 sensors and all of them behind the counter said that they HAD to be replaced and could not be cleaned ....of course they said that about the iac to :rolleyes: :shifty_ey (sounded like they just wanted to make a sell to me ) but i can't remember ,but i think i read a post that someone cleaned their's with electronic spray cleaner and had good results ......maybe someone could shed some light on that .
 






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