Fuel mileage down

jobar · Jan 30, 2014

Hey guys need some answers to my fuel mileage problem. I have a 2001 ford ranger edge 3.0 5speed 3.73's standard cab short box. A few months ago I averaging around 260-290 miles per tank. I looked at my gauge this morning and i am at 75 miles with a little less than half a tank. Something is definitely not right. I have done a full tune up on it a couple months ago and just did an oil change two weeks ago. There is a slight valve rattle that has started accumulating. Any suggestions?

Earl43P · Jan 30, 2014

I had a recurring issue with very light throttle pinging and worse mpg.

Eventually, the CEL came on with a P0401 code, EGR flow insufficient.

The DPFE was the culprit.

One way to tell is to remove the vacuum line from the EGR valve and drive it for a few days. The pinging should go away and after a few drive cycles the CEL will come on.

Replacing the DPFE cured this problem for me, every time.

I don't have this problem any more because I no longer "commute" 4 miles to work. I believe the short duration drive cycles caused moisture to ruin the DPFE. Destructive dis-assembly of the DPFE showed that crystals were growing on the diaphragm, affecting the signal.

Another thought is whether you have ever replaced the O2 sensors (upstream). They tend to get lazy after 60-80,000 miles. The PCM adapts to their lazy signals and the fuel trims will show that if you have the type of code reader that shows live sensor data, like my ScanGage II does.

I have a 2000 3.0 MO5D 4wd with 4.10s and smaller tires. I typically get 340 miles per tank, using about 18 gallons in mixed driving. That's with a 19.5 gal tank.

ab_slack · Jan 30, 2014

Fuel leak?

Fuel gauge getting flakey?

Maybe it wasn't as full as you thought? I know I usually don't see gauge move off top till I've burned 3 or so gallons.

Rearanger · Jan 30, 2014

jobar said:
A few months ago I averaging around 260-290 miles per tank.

Not the best way to calculate fuel usage.

I looked at my gauge this morning and i am at 75 miles with a little less than half a tank. Something is definitely not right.

Neighbor stealing your gas? You'd be running WAY rich with that kind of fuel burning. I'd look at something other than engine using it.

The O2 sensor change did not improve my slightly poorer MPG.

stmitch · Jan 30, 2014

As Rearanger said, using an approximate miles/tank method isn't the best way to compare fuel economy numbers. Really, you should fill your tank, drive until it's pretty empty, record the number of miles you've driven, and then the number of gallons required to fill the tank again. To get your mpgs, divide the miles driven on that single tank, by the number of gallons it takes to fill up.

Second the gas gauge in our trucks isn't always the most accurate. You can't look at it if it's reading half a tank, and say that you've used half your fuel at that point. The only way to find out is to see how many gallons it takes to fill the tank.

To your problem though, the others have brought up good points. Are you sure the tank was completely full? Are you sure there are no leaks, or people stealing gas from your tank? Have you checked your brakes to make sure they're not dragging? Are your tire pressures where they should be?

Also, winter blend fuels kill fuel economy, so comparing your current mileage to what you were getting months ago probably won't look good. I get over 30 mpgs in my daily driver during the summer, but that number drops to around 26mpg this time of year due to the cold temps and winter fuels. Nobody gets better fuel economy in the winter than the warmer months.

jobar · Jan 31, 2014

Earl43P said:
I had a recurring issue with very light throttle pinging and worse mpg.

The DPFE was the culprit.

Another thought is whether you have ever replaced the O2 sensors (upstream). They tend to get lazy after 60-80,000 miles.

DPFE? What is that? I did have a slight throttle pinging but it went away. 02's have never been replaced to my knowledge. Maybe its time.

ab_slack said:
Fuel leak?

Fuel gauge getting flakey?

Fuel gauge is "fairly" accurate. I am putting the same amount in every fill up.

Rearanger said:
Not the best way to calculate fuel usage.

I don't calculate fuel mileage by the tank. I just know that when I looked down,75 miles on a little less than half a tank is way off.

stmitch said:
Really, you should fill your tank, drive until it's pretty empty, record the number of miles you've driven, and then the number of gallons required to fill the tank again. To get your mpgs, divide the miles driven on that single tank, by the number of gallons it takes to fill up.

To your problem though, the others have brought up good points. Are you sure the tank was completely full? Are you sure there are no leaks, or people stealing gas from your tank? Have you checked your brakes to make sure they're not dragging? Are your tire pressures where they should be?

Also, winter blend fuels kill fuel economy, so comparing your current mileage to what you were getting months ago probably won't look good. I get over 30 mpgs in my daily driver during the summer, but that number drops to around 26mpg this time of year due to the cold temps and winter fuels. Nobody gets better fuel economy in the winter than the warmer months.

That is how I always calculate fuel. Tank was completely full. I put in the same amount every fill up. Stealing gas might be a possibility. I don't exactly live in a great neighborhood. Brakes aren't dragging, tire pressure is good. Will the winter blends drop off that much though? I'm only looking at 150 miles per tank. That's not very far. Especially when I was averaging around 260. 100 mile drop off?

stmitch · Jan 31, 2014

It seems unlikely that winter fuels would make that large of an impact, but it may be possible. Like I said, I'm seeing about 6-7 mpg drop in my daily. Based on your numbers, you're about the same. I doubt you guys get the really awful winter fuels down in GA though. You probably get a less extreme mix. And your ambient temps are likely a lot warmer than here in Indiana.

Another thing that just occurred to me is a bad thermostat. If the engine isn't getting up to temp, it can have s serious impact on fuel economy too. Is your heat working normally?

RangahDanga · Jan 31, 2014

I've got a 1999 four-oh and I've got a similar issue. Did a tune up in the fall and was averaging 250 +-10 on a full tank. Now i'm lucky to get 175 on a full tank... Could that just be the winter mix fuel? O2 sensors were all replaced in the last 10K miles, not pulling a CEL (yet) and I've got no EGR. The PCV has been disabled, but it has been since I've owned the truck (previous owner did it).

Not the slightest clue where all my mileage went, is it hiding under a floor mat somewhere? :icon_confused:

And before you ask, nobody is stealing it, I've got 24/7 video recording of my driveway...

SnC RangeR · Jan 31, 2014

I am in the same boat.

jobar · Feb 5, 2014

I'm staring to think my fuel gauge is messing up now. I filled up yesterday and only put 11.2 gallons in it. I have a 16 gallon tank I think. Where's the other 5 gallons?

Fuel mileage down

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