The importance of clean MAF and working O2 sensors!

[WECole]

The importance of clean, working MAF and O2 sensors!

Well, here's something to really drive home how important the O2 and MAF sensor are to good gas mileage...

Since buying my '98 Expedition a couple months ago I've only gotten 10.5 mpg city, 13 mpg highway. The check enigine light has been on with a code for bad upper O2 sensors, but money has been too tight to take care of the problem right away. I knew the issue was affecting gas mileage but since I've just been using the truck for driving to/from work, I just gritted my teeth at the pumps until I had a chance to fix the problem.

This weekend I did a 1600 miles round trip drive to California from my home in Oregon. Before I left I decided to have the 02 sensors replaced, with the hope that it'd improve my mileage by 2-3 mpg. The mechanic that did the sensors also cleaned the MAF sensor and injectors for me - "just in case".

Before repair : 10.5 mpg city / 13 mpg highway (flat roads)
After repair: 16 mpg city / 21 mpg highway (flat roads)

(This was calculated by carefully recording mileage and fill-ups at the pumps during 1,596 miles of driving this weekend).

If I ran the A/C, my highway mileage dropped to 12-16 mpg, depending on if I was driving thru the mountains (we have a lot of 6-7% grades) or if I was driving on flat roads. Even so, driving under the worst of conditions with the air conditioner running still beat the best mpg I was able to get before the repairs.

I knew the O2 and MAF sensors had a big effect on gas mileage, but I didn't realize how extreme it could be, nor how much running the air conditioning would impact it.

My advice to all of you worried about your own gas mileage is to keep my experience in the back of your head next time you're trying to decide if you really want to go clean that MAF or put it off, or if replacing a set of bad O2 sensors is a "high priority" or not...

 

[Captain Morgan]

THX for that!

It's good to get some real world info from others experiences. The cost of the parts and labor will be recouped soon at the pump.

 

[WECole]

The parts and labor were a bit under $220. The trip was 1600 miles. For simplicity, let's just use my highway mileage ...
Pre-repair mileage of 14 mpg hwy (rounding up)
Post repair mileage of 20 mpg (rounding down)

I would have used (1600/14= 114.3 gals of gas) without the repairs
and (1600/20)= 80 gals of gas with repair. With gas price @ $4.05 - I get $485.78 vs $324, so $161.78 is the minimum I calculate I saved just on this trip!

How's THAT for real-world numbers? I just saved at least $162 on one weekend trip!

(And keep in mind that we rounded the old mileage up and the new mileage down, calculated all highway mileage, which it wasn't - and didn't calculate lower mpg for mountain driving or running the A/C, all of which means I would have/did use more than the number of gallons we just calculated, so my real savings this weekend from the better mpg was actually considerably higher!)

 

[Captain Morgan]

I'm stopping by O'Reilly's on the way home %$#@!

 

[WECole]

LOL - makes me want to kick myself for not getting those sensors changed out sooner. I saw someone else post elsewhere in the forums how they were getting like mid-upper 20's for highway mpg and I thought "yeah, SURE you are...", but after seeing such a dramatic improvement in my own mpg with a properly running stock engine, I believe them.

Hmmmm, I wonder what a good programmer/chip could do for me...

 

[98EXeb]

IM guessing I should have mine changed...im getting around 15 mpg city right now. Hmmmm

 

[WECole]

Well, keep in mind that I've been talking about highway mileage (I get about 16 mpg city, right now) and I was getting a check engine light for my O2's, so my case was a bit more extreme than I suspect would be the case for most people (and at about $50 a pop, the O2 sensors are not cheap). I'd certainly suggest cleaning the MAF sensor and possibly running some fuel injector cleaner in your next tank of gas. (BTW, my engine is totally stock except I did the Gott's mod for a little better airflow.)

 

[98EXeb]

Well, keep in mind that I've been talking about highway mileage (I get about 16 mpg city, right now) and I was getting a check engine light for my O2's, so my case was a bit more extreme than I suspect would be the case for most people (and at about $50 a pop, the O2 sensors are not cheap). I'd certainly suggest cleaning the MAF sensor and possibly running some fuel injector cleaner in your next tank of gas. (BTW, my engine is totally stock except I did the Gott's mod for a little better airflow.)

Yeah im all stock too...I guess I could just clean the MAF..thanks for the info!

 

[LameSuburbanDad]

remember, only replace the o2 sensors if your computer tells you too, don't drop $120 or more if you don't have to. the MAF however you can clean at home can't you?

 

[superexpy]

Dang... I get only 15mpg HWY or at least thats what my thingy above the windshield says. How acerate is that gauge anyways?

 

[TexasAngel34]

Ok im gonna sound stupid , whats MAF? Is it air flow .... lol... wanna know what it is i need to change

 

[WECole]

MAF is mass airflow sensor - it's built into the air intake tube, just after the air cleaner. A little carb cleaner carefully sprayed onto the two wires of the sensor cleans it nicely, but be careful because the wires are thin and easily broken if too much force is used on them - never try to touch them directly.

 

[catmaster25]

question...

Is a $270 jet MAFS... Worth it in yalls opinion? And what are Gott's mods???? I've done a little research online but not much YET, I feel like my expo is holding back after adding headers and a k&n CAI.