Fuel mileage and Codes | Ford Explorer Forums - Serious Explorations

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Fuel mileage and Codes


May 30, 2000
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Now...I really don't know wath to do!!
My truck is doing 12 MPG (highway or town).
I have changed the fuel pressure regulator(99 CDN $$) and made a complete tune up.(Filters, plugs... everything.). I tough of the O2 sensor but haven't had no codes for it.
Talking about codes, I had a code 542: fuel pump secondary circuit problem. Could have something to do with my 12 MPG but what???

Help me please!!
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92 Sport 4X4
88 Bronco II 4X4

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I am running into the same sort of trouble you are Francis, I have changed or checked EVERYTHING, including my O2's. I don't believe this is it, but i also run 30"s BFG AT's, but I don't believe they would be the culprit with my mileage being as bad as 10-12 mpg. I had my uncle, who is EXTREMELY mechanically inclined(he built race cars in the good old days) check the fuel pressure regulator, it was fine, I replaced the O2's, and noticed a slight improvement, but nothing much. Whats to give? I am a college student, and if it keeps this up, I am going to (!!GASP!!) sell my baby and get a Nissan Maxima SE, so I don't have to take out a loan to pay for gas.!! As my bill last month was $200!!!!!!!!! Please help us!!!!

'94 XLT - 30" BFG AT's
Dynamax Exhaust
K&N Air Filter
Modified Air Box
"He who takes no risk, takes no glory."

Since 2 weeks, I have been checking for a
leak in my fuel system but nothing, no smell... IM going to take a shot at the O2S. I have cycling temp problems but I don't think it could bring my MPG down from 18-20 to 12...

I keep trying....

92 Sport 4X4
88 Bronco II 4X4

Are either of you in an area where you are running oxygenated fuels? My dad and a few other friends live in an area which requires oxygenated fuel and their mpg is dropping approx. 33%. 15 down to 10. 24 down to 17.
Just a thought.

Oxygenated fuel???

Never eard of this before... We don't have this in Quebec(Montreal).

Thanks tough!

92 Sport 4X4
88 Bronco II 4X4

Does NY state have oxygenated fuel cause when I filled up in NY state I got 18.5 mpg and when in NJ I get around 13-14. I have 235 bfg's All terrain, splitfire dual core, bosch plat+4', K&N with a modifyed air box.
I need help!!!

'93 XLT 4 Door 4x4

I am also experiencing the same problem. Bad gas mileage 11-12 mpg city. No codes. Engine runs fine. No smell of unburned fuel. No soot in exhaust. Fuel pressure regulator tested and was fine. Never heard of oxygenated fuel. One would think that by adding oxygen in the fuel that you would get better combustion therefore an increase in gas mileage. Perhaps Xplorers just eat gas in the cold weather. This is what I am coming to believe. As soon as the weather warms up, the gas mileage goes back to normal.

However if someone the answer to our dilema......please pass on the info....cause my wallet is hurtin for certain. thanx.


doo doo happens

Kind of a long shot, but what about your thermostat? If it is sticking open, your engine will not warm up enough for it to run correctly. The computer senses the temp of the engine and will then adjust the mixture (cycles) of the injectors. As the engine warms, the mixture or cycle will cause it to run leaner.

Another idea is a coolant temp sensor. I am not sure they have one but would assume they do. Just am not sure where to find it. Someone else may be able to help in this part.

It was just a thought since it does better in the summer.

91 XLT 4x4

My temp gage had been reading low for quite a long time accompanied by an occasional CHECK ENGINE light after climbing up to about 4,000 feet. I finally put 2 and 2 together and thought that I had a stuck open thermostat which I replaced. This fixed the gage problem, but now my Average fuel mileage on the computer dropped from 16.5 to about 15.0. I would have thought the mileage would have gone up. Any ideas?

'95 Eddie Bauer

[This message has been edited by DonL (edited 04-22-2000).]

Have you checked and changed your fuel filter? It can get clogged making your fuel pump work harder. I recently changed my fuel pump because the fuel level sender went dead. I noticed a drop in mileage with my old fuel pump - from 20mpg to 15mpg mostly highway driving. After I replaced the fuel pump, the mileage went back up to 20mpg range again. I don't know if the old pump was failing because I didn't notice any performance losss except for my mpg, but I'm glad its back up again. Hope this helps.