Disconnected MAF sensor - worst mileage

paulrc · **Joined:** Mon Aug 06, 2012 7:14 pm **Posts:** 22

When I pull the MAF sensor in order to turn off the EGR valve, my mileage actually decreases. Its pretty significant on the highway - less than 15 mpg. I did a 100 mile drive going 84 mph and it took half a tank from me. Did this twice. Anyone explain to me why this happened? I know i am supposed to get better mileage with the MAF sensor pulled off.

skates04 · **Posted:** Sun Jan 13, 2013 12:51 am

Probably can't expect good mileage doing 84mph either way.... If you did it twice you should have kept it plugged in one of the time to compare.

Dennis MacGyver · **Posted:** Sun Jan 13, 2013 1:16 am

Your best mileage will be at 1800 rpm's in 5th gear..

paulrc · **Joined:** Mon Aug 06, 2012 7:14 pm **Posts:** 22

skates04 wrote:

Probably can't expect good mileage doing 84mph either way.... If you did it twice you should have kept it plugged in one of the time to compare.

I wrote my message unclear. I'll write with more detail

On my CRD, I have over 150,000 miles on mine, when I drive 84 mph I get my best mileage on long distance trips. at 84 mph I get a little bit better than 30 mpg, this is at roughly 2200 RPM. From Colorado springs, CO to Los Angeles, CA I drove 84 mph through mountains and hills for 90 percent of the trip and averaged 30 mph on two occasions and once from albuquerque, NM to Los Angeles, CA with the same results.

When I disconnected the MAF sensor, my mpg dropped significantly. I did that on two different occasions and got worst mileage, avg about 10 mpg. Reconnecting the MAF sensor the mileage went back up.

What reasons would cause this?

Dennis MacGyver · **Posted:** Sun Jan 13, 2013 6:48 pm

paulrc wrote:

skates04 wrote:

Probably can't expect good mileage doing 84mph either way.... If you did it twice you should have kept it plugged in one of the time to compare.

I wrote my message unclear. I'll write with more detail

On my CRD, I have over 150,000 miles on mine, when I drive 84 mph I get my best mileage on long distance trips. at 84 mph I get a little bit better than 30 mpg, this is at roughly 2200 RPM. From Colorado springs, CO to Los Angeles, CA I drove 84 mph through mountains and hills for 90 percent of the trip and averaged 30 mph on two occasions and once from albuquerque, NM to Los Angeles, CA with the same results.

When I disconnected the MAF sensor, my mpg dropped significantly. I did that on two different occasions and got worst mileage, avg about 10 mpg. Reconnecting the MAF sensor the mileage went back up.

What reasons would cause this?

Is this the mileage according to your EVIC overhead console, or is this mileage based on hand calculations of gallons and odometer ?

kjjet · **Posted:** Sun Jan 13, 2013 8:21 pm

paulrc wrote:

When I pull the MAF sensor in order to turn off the EGR valve, my mileage actually decreases. Its pretty significant on the highway - less than 15 mpg. I did a 100 mile drive going 84 mph and it took half a tank from me. Did this twice. Anyone explain to me why this happened? I know i am supposed to get better mileage with the MAF sensor pulled off.

With the MAF sensor pulled. yes the EGR will be disabled but you may not see any increase in fuel mileage. It is a small amount. Going on a 100 mile drive at 84 mph. You should have a rod sticking out the side of the block. Diesel's dont like high RPM.

paulrc · **Joined:** Mon Aug 06, 2012 7:14 pm **Posts:** 22

Dennis MacGyver wrote:

paulrc wrote:

skates04 wrote:

Probably can't expect good mileage doing 84mph either way.... If you did it twice you should have kept it plugged in one of the time to compare.

I wrote my message unclear. I'll write with more detail

On my CRD, I have over 150,000 miles on mine, when I drive 84 mph I get my best mileage on long distance trips. at 84 mph I get a little bit better than 30 mpg, this is at roughly 2200 RPM. From Colorado springs, CO to Los Angeles, CA I drove 84 mph through mountains and hills for 90 percent of the trip and averaged 30 mph on two occasions and once from albuquerque, NM to Los Angeles, CA with the same results.

When I disconnected the MAF sensor, my mpg dropped significantly. I did that on two different occasions and got worst mileage, avg about 10 mpg. Reconnecting the MAF sensor the mileage went back up.

What reasons would cause this?

Is this the mileage according to your EVIC overhead console, or is this mileage based on hand calculations of gallons and odometer ?

Hand calculations of gallons and odometer. The dashboard says I'm going 86mph but its a little fast, my cruise control does not let me set it in faster than 86 mph which is really 84 mph. When I drive in the 70-75 mph range on trips less than 100 miles, I get around 26-27 mpg. Trips over 100 miles, I get much better mileage. I'm still proud of to this day is that it only took me 36 gallons to get from Colorado Springs to los Angeles.

paulrc · **Joined:** Mon Aug 06, 2012 7:14 pm **Posts:** 22

kjjet wrote:

paulrc wrote:

When I pull the MAF sensor in order to turn off the EGR valve, my mileage actually decreases. Its pretty significant on the highway - less than 15 mpg. I did a 100 mile drive going 84 mph and it took half a tank from me. Did this twice. Anyone explain to me why this happened? I know i am supposed to get better mileage with the MAF sensor pulled off.

With the MAF sensor pulled. yes the EGR will be disabled but you may not see any increase in fuel mileage. It is a small amount. Going on a 100 mile drive at 84 mph. You should have a rod sticking out the side of the block. Diesel's dont like high RPM.

Everything I've read I assumed I should get better increase in mileage. I've always felt that my vehicle runs best above 75mph. Nice open highways in northern CO, Wyoming, and Utah allow you to drive fast.

bentstrider83 · **Joined:** Sat Jan 05, 2013 1:43 am **Posts:** 42

Before a trip about a week ago going from Clovis to ABQ and back, I unplugged the MAF and noticed a dip in MPG compared to when I first drove it down from Denver to Clovis unaltered.
This of course was going off of "full-tank" to Odometer calculations mind you.
I was already nearing half-a-tank of fuel burned once I got to the interchange of the 25/40 freeways.

A few days after that trip, I had to go from Clovis to Lubbock and back.
Prior to this trip, I pulled the MAP sensor out from its spot and checked it out of curiosity.
It had a substantial deposit of soot and other carbon particles built up on it and I got to cleaning it up per the n00b guide.
A little bit after that, I reinstalled it and got cracking on my trip.
This time, the total round-trip was about 220 miles(around the same distance I drove from Clovis to ABQ) and only a little over a 1/4 tank was used.

Check that MAP sensor and clean it up!!

kjjet · **Posted:** Mon Jan 14, 2013 4:34 pm

For what I have seen the CRD gets the best MPG when the RPM is under 2000.

What is your engine temp? Should be at 1/2. If it's lower, your T-stat is bad and will give you worse MPG.

Other things that will effect MPG.

1. Weather, rain, wet roads, snow & temp.
2. How often you change speeds due to traffic. Use speed control.
3. Roads, hills, construction.
4. Type of fuel. Some use a winter blend.
5. Clean air filter.
6. Clean fuel filter.
7. Clean MAP sensor.
8. Tires, worn or under PSI
9. Using airconditioning or defrost.
10. Stuck or broken emergency brake. (Jeep gave us a real nice E- brake "NOT")

Just to get started.

Disconnected MAF sensor - worst mileage

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