Poor MPG?

[RandomNerd2000]

So, all has been well with my 01, other than the wheel bearing a little ways back, I've been driving it, and I decided to change the air filter because it just didn't look good, now my MPG is 16.7 with 75% highway driving, and that seems really low, but I'm curious, where's a good place to look sensor wise? It's not normal for a new air filter to hurt the MPG average. The CEL isn't on and my fuel trims are 4% on one bank and 6% on the other at idle.

 

[koda2000]

Have you replaced the pre-cat O2 sensors?

 

[Mr. Alligator]

Agree that air filter change should not reduce mileage. However, unless you were paying very careful attention to speeds and distances, you might not have an actual mileage.

Also agree that oxygen sensor issues can greatly reduce fuel mileage. But shouldn't that show on a code read?

If you don't have any codes, I would look carefully at tire pressure and driving habits.

Hope you do find a resolution.

 

[RandomNerd2000]

I'm running 35 PSI the whole way round, I'm wondering if I have a O2 sensor failing, at 191K miles, being run lean a long time, factory plugs, and just age, I'd imagine they are failing, despite no codes, I drive the same road back and forth, and I'm using the MPG monitor because it's an Eddie Bauer, and judging by the float level, it's accurate. I'll probably swap the sensors sometime this week, and get back to the thread with the results.

 

[Mr. Alligator]

if those O2 sensors are original, they are almost certainly ready to be changed.

Impressed also with your paying attention to your engine and monitoring details.

Your Ford will last as long as you want it to last!

Good luck, and looking forward to seeing what the O2 sensor swap does.

 

[koda2000]

In my experience worn out O2 sensors don't always throw codes. I had another thought. Hows your thermostat? Can you check your actual coolant temp?

 

[RandomNerd2000]

Thermostat was new in July, the live data shows on average between 180-190 degrees running warm, the sender for the PCM was new in July too, so it's accurate, the cluster also goes to the perfect spot. I know the O2 sensors have been abused, I've heard lean and bad plugs is hard on them.

 

[jmvb]

Honestly, I quitted to have a decent MPG

I tried everything:
- Filters
- Spark plugs
- Spark plugs cables
- Upper and lower intake manifold gaskets
- 02 sensors
- IAC clean
- IAC change
- EGR change
- MAF cleaning
- Air temp sensor cleaning
- Throttle body cleaning

I never had get more than 12 MPG in city and maybe 16 in highway (never more than 60mph)

No check engine, the scanner say that I have good fuel trims (no more that 3%)
The smoke test are all passed.

(I have 31X10.50R15 tires)

 

[jd4242]

Honestly, I quitted to have a decent MPG

I tried everything:
- Filters
- Spark plugs
- Spark plugs cables
- Upper and lower intake manifold gaskets
- 02 sensors
- IAC clean
- IAC change
- EGR change
- MAF cleaning
- Air temp sensor cleaning
- Throttle body cleaning

I never had get more than 12 MPG in city and maybe 16 in highway (never more than 60mph)

No check engine, the scanner say that I have good fuel trims (no more that 3%)
The smoke test are all passed.

(I have 31X10.50R15 tires)

What gears?

 

[jmvb]

What gears?

98' 4x4 XLT 4.0cc SOHC

 

[jd4242]

98' 4x4 XLT 4.0cc SOHC

Thats not gears..like 3.55 or 3.73

 

[jmvb]

I don't know... standard ones I guess

http://www.ford-trucks.com/forums/vindecoder.php?vin=1FMZU34E8W4B47053

 

[jd4242]

I don't know... standard ones I guess

http://www.ford-trucks.com/forums/vindecoder.php?vin=1FMZU34E8W4B47053

Look on your door tag..you probably have the wrong gears for the tires..you need 4.10 if you want your mileage back

 

[jmvb]

 

[jmvb]

3.55 if I'm correct

 

[jd4242]

3.55 if I'm correct

There is your problem then..should have atleast 3.73 for 31s,honestly 4.10 would be best especially if you dont go over 60 and dont do alot of highway

Also have you adjusted your speedo for tire size??

 

[jd4242]

Thermostat was new in July, the live data shows on average between 180-190 degrees running warm, the sender for the PCM was new in July too, so it's accurate, the cluster also goes to the perfect spot. I know the O2 sensors have been abused, I've heard lean and bad plugs is hard on them.

Lean conditions can kill mpg..also have you cleaned your maf??

 

[jmvb]

There is your problem then..should have atleast 3.73 for 31s,honestly 4.10 would be best especially if you dont go over 60 and dont do alot of highway

I would need 3.73 in both diff?

 

[jd4242]

I would need 3.73 in both diff?

Yes if 4x4 but unless you find a donor vehicle the cost wouldnt be worth it..unless you drive alot.id try and find a truck with 4.10s if you can,it would be more worth the hassle

 

[RandomNerd2000]

3.55 if I'm correct

I'm running 31s on 4:10 gears, it's seemingly a good balance.

Lean conditions can kill mpg..also have you cleaned your maf??

I have actually, which brings me to my next post, I've cleaned the MAF in this car twice, and I looked at the live data this morning, both the upstream O2 sensors were switching properly, nothing out of normal, so I thought about it, and decided that since the old air filter didn't seal perfectly, box was a bit loose, new one seals fine, that it might be an issue with the sensor itself since the the box hadn't been sealed, so I took some old junk wheels for scrap and picked up a $5 sensor out a 99 Sport with 136K miles, cleaned it, and installed it, and it's seemingly fixed, doesn't smell rich and feels a lot smoother and has more power at road speed, so the old sensor had to about be damaged. I figure the MPGs will go up now since in theory, the sensor was causing a false lean.