Ford V10 gradual reduction in fuel economy

[whemme]

I have a 26' Class C on a 2000 Ford E450 chassis with V10 engine now with 115,000 mile on it. I used to average 8.5 mpg pulling a 3400 lb toad but over time the economy has deteriated to the 7.5 to 8.0 mpg range. My Ford dealer says that as long as I am not getting any check engine codes that my oxygen sensors are still OK and not causing the reduced mpg problem. But I still wonder if the oxygen sensors might be causing the problem. Anyone else with experience with this issue?

[whemme]

My V10 at 115,000 miles used only about 1 qt oil in 4000 miles.

[Chum_lee]

"My Ford dealer says that as long as I am not getting any check engine codes that my oxygen sensors are still OK and not causing the reduced mpg problem."

Yep, that's what they will tell ya! If there aren't any fault codes, many of the "technicians" of today are literally . . . . . lost.

At 115,000 miles, is your engine using any oil? Say, . . . . more than a quart every 750 miles. If you can't find anything else, it might be worth checking to see if your catalytic converter is getting plugged up. When cold, hit it with your hand and listen for rattles. (broken honeycomb substrate) If no, then removing it and shining a flashlight through it will tell you right away if there is a flow problem. While you are down there, check the entire exhaust system for dents, crimps, etc.

Chum lee

[clayway]

I have no idea whether this will work for you, but here in FL many stations have no alcohol fuel, mainly for the marine motors, I have been filing up using this fuel, no
more pinging & better mpg

[pnichols]

:h

Wow ... so nowadays we have to change several coils ever so often (which I have to hire done for $$$$) ... instead of one coil, one set of distributor points, and maybe a set of spark plug wires ever so often (which I could easily do myself for $).

I guess I understand that???????? :S

P.S. I'm not interested in hearing any reasons/excuses as to why "individual coils per plug" is some kind of advance in non-diesel fossil fuel engine technology. One can always come up with explanations as to why us common folks should have to spend more money to get by.

[whemme]

Total cost at my Ford dealer to replace 10 spark plugs and coils, fuel filter, serpentine belt and oil pressure sensor was $1,776.53 back on Feb 2017 at 99,167 miles.

[Kamphiker]

whemme wrote:
Yes the spark plugs and coil overs were actually replaced with new. I happen to know the Ford mechanic that did the work. Boy those coil overs are expensive - about $95 each for 10 of them!!!!

Did that include Labor ?

I recently replaced all 10 coils & Plugs on my 2006.
Genuine Motorcraft coils were $ 24.00 each. Amazon Motorcraft Coils for V10

Changing out was a PITA. I now know why Dealers charge between $ 1,000 & $ 1,200.00 to change coils & plugs.

[whemme]

Yes the spark plugs and coil overs were actually replaced with new. I happen to know the Ford mechanic that did the work. Boy those coil overs are expensive - about $95 each for 10 of them!!!!

[time2roll]

My plugs on my 5.4 were changed at 120,000 with no change to economy, smoothness of running or power. It ran exactly the same. And yes I know the dealer actually changed them.

I also would lean on more E10 and possibly some loss of compression.

[carringb]

whemme wrote:
New spark plugs and all new coil overs were installed at 100,000 miles but that did not help the mileage problem.

Have you verified they were actually done?

[Rick_Jay]

whemme,

Ok, I'll probably take some flak for this, but over the years, have you been using less "real gas" (no alcohol) and more of the E10? On all of our vehicles, the miles per gallon drops just about 10% on the E10 gas we get all over the east coast.

When we first got our motorhome, our gas stations had real gas and that's what I uased. When the E10 was mandated and I had to use that, I noticed our mpg dropped from the ranges of 8-9 mpg with real gas (depending upon whether we were towing or not) down to 7-8 mpg when we used the ethanol stuff.

I wasn't sure what had happened, but about 5 years ago when we were travelling south, I apparently filled up at a station which had real gas. Once back on the road, I immediately noticed on my dash computer the average mpg numbers began climbing to almost a full 1 mpg more! Terrain had been the same, so it wasn't a "you're going downhill" reason. The next fill up was with E10 and down came the numbers.

You've got A LOT more miles on your rig than ours (about 40,000), so it is certainly possible you're having issues due to aging components.

Just a thought.

Good Luck,

~Rick

[T18skyguy]

Try cleaning the MAF sensor. Easy to do, just buy the correct spray from the auto parts store. It's easy to check the O2 sensors, they should read out a certain ohm reading on your multimeter. Youtube has a video on it I'm sure.

[whemme]

New spark plugs and all new coil overs were installed at 100,000 miles but that did not help the mileage problem.

[DrewE]

Have the spark plugs been replaced? If not, they're probably at (or beyond) the end of their useful life.

Oxygen sensors do age, and are relatively inexpensive and easy to replace. If they're only somewhat out of calibration they may not cause check engine lights but still affect mileage some (and possibly catalytic converter life), or so I've been led to believe. Replacing them might be a reasonable thing to try. For that matter, if the catalytic converters are getting plugged from soot or whatever, that can affect engine performance as well.

[ron_dittmer]

Hi whemme,

Check for this.......It is possible someone who worked on your rig made this easy mistake, causing poor fuel economy and poor performance. It is easy to check for.

Pop-off the oval air intake from above the radiator and pivot it upward. Look into the hole where it was snapped into. If you see a black plastic flap that interferes with the flow of air, you need to remove the black plastic shroud above the radiator and fold the flap back while resetting it into position.

There was a recall in 2010 on that flap. Apparently a new-bee line worker was not holding the flap back when installing the black plastic top radiator shroud. It is conceivable that an unsuspecting mechanic could make the same mistake. I almost made that mistake myself on our 2007 E350 when reinstalling the top shroud after removing a bird that died hitting and getting lodged into our front grille area.