Stumped by random gas guzzling.....what did i do?

[ezrider440]

hey there folks
I have an interesting problem, I've read a bunch of search threads and still come up with my hands open and empty. My 96 explorer with the 5.0L and 2 wheel drive, has began to stuck gas i like suck coffee. I was averaging somewhere around 15-16 mpg in the city now i am around 6-7 mpg, I don't have a lead foot, slow starts nothing over 2000 rpm, 60 on the highway. the truck is in great shape ( knocking on the metaphoric wood). the plugs/wires are new within the last 6 months, new filters and fuilds, all four new oxygen sensors are new, the entire suspension is rebuilt. she runs strong, pulls hard...........so what can it be? there are no codes..........what could it be? anyone have anythoughts? my guess is bad gasoline but what are the odds of getting three bad tanks of gas in three different gas stations? I run regular octane

Thanks in advance

 

[carlover]

Try a seafoam treatment, then reset your pcm and see if that helps.

 

[Turdle]

Oh--hey
Your torque converter may not be locking--

Try this--get on the highway, and achieve a nice steady 65 mph. How many rpm's is your tachometer indicating at this speed?

 

[toypaseo]

Underinflated tires?

Alignment off?

 

[JDraper]

Dropping from 15-16 to 6-7 is pretty drastic. Wouldn't think alignment or low tire pressure would move the mileage that much.

I'd be inclined to check the fuel pressure regulator. When they go bad, the truck can really suck fuel down. The fpr is on the rear of the intake manifold, and is a small vacuum controlled silver dashpot. One of the signs of a bad FPR is if there is gas in the vacuum line.

 

[ezrider440]

hey gents
thanks for the quick responses..........no aligment is dead on center and wouldn't cause so much trouble, tires are inflated to 40 psi in rear and 35 in front, not an issue.
the rpm range hasn't changed at 65 i am running almost 1900rpm which is what is always was, but the fuel pressure regulator is a valid idea, i'll fool around with it, i'll check my fuel pressure if it's too high then it makes sense. any other ideas?......

thanks for the help always appreciated....i wouldnt have thought of the FPR

 

[JDraper]

... i'll check my fuel pressure if it's too high then it makes sense. any other ideas?......

thanks for the help always appreciated....i wouldnt have thought of the FPR

Fuel pressure doesn't have to be high if the fpr diaphragm is cracked. It will suck fuel into the vacuum line (and then into the motor) instead of going into the fuel rail. That's one of the causes of excess fuel consumption.

 

[KPT]

Does the temp gauge show the engine getting to the normal operating temp? My thermostat was stuck open and I gained 2 mpg when I replaced it.

I don't think that would cause the loss you are getting though.

 

[DeRocha]

How are you determining gas mileage? 6mpg is a huge amount to drop down too. Is someone "Borrowing" some gas at night via a siphon hose?

 

[palmer302]

How are you determining gas mileage? 6mpg is a huge amount to drop down too. Is someone "Borrowing" some gas at night via a siphon hose?

Could be a leaking gas tank too. Had that problem in my truck that I dont drive too often. I thought somebody was stealing my gas until I noticed a small wet spot under the fuel tank.

 

[Tbars4]

try a locking gas cap if only temporary...hi gas prices and all...

 

[Minivek]

would a cracked fpr diaphragm and/or busted fpr show up during a fuel pressure test, and if so, how so Would it vary according to speed or under acceleration etc (other than the fact more fuel is injected, that I understand). Thanks.

 

[JDraper]

would a cracked fpr diaphragm and/or busted fpr show up during a fuel pressure test, and if so, how so Would it vary according to speed or under acceleration etc (other than the fact more fuel is injected, that I understand). Thanks.

Not sure if it would show up or not. It would depend upon the severity of the crack in the diaphragm. The pump is capable of putting out considerably more pressure than the injectors need. The FPR drops the pressure to the correct level for the injectors, so if it's got a cracked diaphragm, it may show normal pressure because the extra capacity of the pump is just pushing fuel through the diaphragm into the vacuum line. Best way to check is look for presence of fuel in the vacuum line.

 

[Minivek]

Will do. thanks

 

[ezrider440]

well, sorry to keep you'all waiting, had to take care of some medical issues, but i checked all the vacuum lines, they are clean and i pump checked them, it shows a slight drop of vacuum 2-3 psi after about two hours of standing. so i wouldn't think it's vacuum issue.
at this piont i really don't know, it runs great, all vital signs are normal, i doubt there's a gas leak this is a work truck for me so everyday is at least a 50 mile drive, plus i keep it in a clean concrete driveway or marble floored garage..so i notice any leaks,
one thing thats iffy is the fuel gage, sometimes it's not too accurate, but i gage my fuel by gallons per miles driven, i know that 200 miles moslty in city drving, meaning stop/go, slow traffic after driving 220 miles i should use 14- 15 gallons from a full topped off tank ( 15.5- 16 mpg) now i am about 100 miles out of 16 gallons. and on the highway loaded down with usually many 500-700 pounds of cargo, averaging 65-75 miles per hour, i'd use up about 16-17 gallons for 300 miles........now i can't break 200 miles.

I am really stumped

thanks folks any help is appreciated

 

[Tbars4]

i still say try a locking gas cap to eliminate the obvious...trust me, i have gone thru this very same thing and it was answered as soon as i ran one tank with it on...you might also look at your hoses to your tank...i've had one on top that was not sealed proper and it let gas go over the tank when it was full and driven...i never even smelled the gas...but again, try the cap if only for temporary...