Gas mileage cut almost in half!!! what could it be??

[Turdle]

2500 is kind of high I think-mine is exactly 2200 rpm's at 70 mph
There is a label on the driver door jamb. What is your axle code?

 

[askingxforxit]

2500 is kind of high I think-mine is exactly 2200 rpm's at 70 mph
There is a label on the driver door jamb. What is your axle code?

3.73 LS

 

[Turdle]

Mine also-
I think the torque converter is not locking.

 

[askingxforxit]

well what is more likely?? Torque converter or O2 sensor?

Just over 90k btw

 

[redneck21]

I think a bad o2 would throw a code. take them off and spray them with a lil brake dust cleaner and see if that help.

 

[Turdle]

Well,
either the torque converter is not locking, or, the truck is straining against something, which is causing the excessive engine speed.
I had an issue a while back which was eliminated through tuning. Keep in mind My engine is modified, and I am using different maf sensor. My issue was induced.
However-bringing back the point, my torque converter would quit locking after the truck went through a few bouts of surging. The only indication I had was high rpms at cruising speed. There were no codes at all.
A reset of the PCM would "cure" it for awhile.
I haven't had the issue arise since James fixed it.
However-it does make a point. The torque converter can fail to lock without setting a code.

It would be interesting to log data with an xcal2 to see the torque converter lockup command, and if it is indeed happening.

Now
Going deeper

The Maf sensor can mess with transmission functions-you might try cleaning it-and resetting the pcm again.??
Another thought would be to check the TPS for a smooth signal

 

[shortstack]

The RPM's should be closer to 2200-2300 at that speed.

Sounds like the torque converter is not locking--this will eat gas like crazy man!!

try this-
disconnect the battery for a few minutes, and go for a drive. See if the RPM's don't settle down after a reset.

that seems low to me, mines around like 2300 - 2400 @ 65mph but then again my gears are 4.10, not sure if that makes a difference

 

[Turdle]

that seems low to me, mines around like 2300 - 2400 @ 65mph but then again my gears are 4.10, not sure if that makes a difference

No, it isn't, and yes it does.

 

[askingxforxit]

I think a bad o2 would throw a code. take them off and spray them with a lil brake dust cleaner and see if that help.

According to the trusty Haynes manual it says DO NOT use cleaners on the o2 sensor.

Anyone else try this? I have the cleaners so I'll try cleaning the MAF first and wait for a reply on the o2 cleaning.

 

[corkey]

i have the same gear in mine and it doesn't rev that high at 70,, unless the overdrive is off, i would go with the non locking tourque converter,, i only turn about 2100 at 70 mph,,

 

[askingxforxit]

Would there be any other signs of a bad torque converter??

Just cleaned the MAF, IAC looks brand new and I cleaned the TB just for fun( it was pretty nasty. Until I hear more on cleaning the o2 sensor I'll hold off on that. Going on a test drive!!

UPDATE:

O/D off 60 MPH approx. 3000 RPM
O/D on 60 MPH approx. 2100 RPM

 

[Willard]

The torque converter wouldn't necessarily be bad, but if it was, there would be other problems. The problem is likely the solenoid in the transmission isn't locking the torque converter. This could be either the solenoid, or something else wrong causing the computer to not send the signal to lock up.

 

[askingxforxit]

The torque converter wouldn't necessarily be bad, but if it was, there would be other problems. The problem is likely the solenoid in the transmission isn't locking the torque converter. This could be either the solenoid, or something else wrong causing the computer to not send the signal to lock up.

A solenoid sounds a lot better than a bad TC. How would I be able to test his?

I'll have to bring my volt meter home from work sometime this week to check the TPS.

 

[askingxforxit]

I just read thru an old thread about poor mileage and one thing mentioned was sea foaming the gas and intake system. Any more info and help on this would be great! Being that I drive 60 miles a day for work I need all the mileage I can get with an X at the moment....until I start the mods

One thing I just remembered that may or may not be a factor. Usually I fill up at an Arco gas station by my work and when I filled up ( in post #1) I was at a Shell station by my house. As I've read in other threads there have been mileage issues with "winter gas" though I highly doubt that is an issue because I live in southern California. Our winter lasts about a month!! haha

 

[redneck21]

According to the trusty Haynes manual it says DO NOT use cleaners on the o2 sensor.

Anyone else try this? I have the cleaners so I'll try cleaning the MAF first and wait for a reply on the o2 cleaning.

I did it b4 with a Honda and an doge trunk it didn't mess them up but just it didn't mess mine up doesn't mean it won't mess them up i might have just got lucky. Since it drys fast and doesn't leave and residue i thought it was ok.

 

[askingxforxit]

I did it b4 with a Honda and an doge trunk it didn't mess them up but just it didn't mess mine up doesn't mean it won't mess them up i might have just got lucky. Since it drys fast and doesn't leave and residue i thought it was ok.

Well even if I ruin them I'm sure they are due for replacement with 90k miles.

I wont be able to test the mileage until I drive to work tomorrow. Thanks to everyone for the tips and advice thus far!!!

 

[askingxforxit]

How many o2 sensors btw?? I just noticed my manual is for 1991-99 explorers and mine is an 01. I used to have a 99 thats why I have the old manual, looks like I need to get a new one:

 

[Turdle]

I think you are taking a wrong turn with the 02 sensors-
I'd focus on the engine speed issue. That's where your mileage is going south.

Your truck has 4- 02 sensors,

 

[askingxforxit]

I think you are taking a wrong turn with the 02 sensors-
I'd focus on the engine speed issue. That's where your mileage is going south.

Your truck has 4- 02 sensors,

Then maybe a problem with the intake manifold?? Vacuum leak?? I'll hold off on the O2 until I do a good tune up then.

 

[Glock40cal]

Have you verified that the gas Gage is correct and not giving you a false reading. I'm not sure about the Fuel pumps on the X but i know on some trucks that an early warning sign that the fuel pump is going out is a floating/non working fuel Gage. My X's gas Gage is kinda retarded. One moment Its looking like at a half a tank I'm getting terrible gas mileage, then it takes forever for it to get to empty and my mileage is right where it has always been. A tank later and its acting normal.