Your description of the RPMs and when and how they are jumping around is incomplete without any input on what the speed or trans is doing at those times. If the RPMs are changing drastically without the trans shifting or vehicle speed changing then something is not right.
As for the shop visit, I would explain what's happening vs what used to happen then go for test drive with him riding shotgun while you make the rig do what you described, then have him drive it and go from there.
Is the trans hitting all 4 gears and them dropping another couple of hundred RPMs as the TC locks up?

 

Something is seriously up. Even with my horrendous habit of idling my Ex for Hours a day in the winter, when also running in 4x4 24/7 for 6 months with a serious lead foot the worst I've ever seen is 6.5 MPG, typical around town is 8.5 - 9 and highway is 11-13 mph with my current wheels.

 

So, after changing the fuel filter and cleaning the MAF I took the Ex to the transmission shop for my 2 week (ish) checkup.

The shop was at least really cool and one of the workers jumped in with me as we went on a test drive. I told him it appeared as though the RPM's would jump faster than my old 04 excursion and this one with the older transmission (meaning before it was always a steady climb in RPM as the truck gained momentum.) I also said how it felt as though it almost lacked power in 1st gear as compared to my 04 and this 05 with the old transmission. Both are pretty minor and the guy said he felt as the transmission ran well. When we got back, the shop owner who is the builder then took it for a drive and he also said it runs great. I'm always leery they are just telling me this to get me out the door.

On Sunday night and Monday I was able to put in 100 miles of mostly freeway driving and I got 10.5 mpg then Monday night and this morning I was able to put on an additional 156 miles of freeway driving and I got 10.4 mpg.

It sucks because I don't really have any reason to go on these drives other than to see how my MPG is doing.

Than said, I guess that is better than the 7.3 I got the week before with mix of city and freeway. However, because I got 4.5 with city only and 10.5 freeway maybe 7.3 is the "mix" MPG. I still don't feel good about this, but don't know what to do.

I do feel okay ruling out the transmission, but what else can it be?

Thanks again for everyone's help! I truly appreciate it.

 

i had an rpm issue on my 88 f150 years ago with rpms going way up to 4-6k before taking gears an found it was a lose/disconnected wire on the trans to control the gear shifts with rpms not to sure how 2000+ handle the shifting but wouldnt hurt to have a look for any lose or unplugged wires as for fuel only other thigns i can think of would be a possible rusty fuel line on the frame that isnt dripping but is letting the fuel soak through the rust an evaporate so you dont see any dripping

 

Dumb question, but have you ruled out the brakes? Any rims feeling warmer than the rest?

 

I think the shifter is good. I have a new transmission and they did a good job with the shiftier. I doubt the fuel line is rusted because i've been under there a lot and I didn't see any signs of any rust. Also, 1) it almost never snows here and 2) when it does, they either don't use any salt on the roads or they only salt roads I never drive on.

That being said, i will surly climb under and give it one more look. Thanks for the suggestion.

 

That had crossed my mind. I have not noticed any smell or pulling and I had just put on new pads, rotors and calipers not too long ago.

However, at this point, I might as well take the tires off and look them over.

Thanks for the suggestion!

 

the cables i mentioned dont connect to the shifter itself from what i had to fix before they were sencors off that told the trans when the engines rpm was right to shift i would imagen its the same idea of sensors and electric connectors giving the trans a signal for when it needs to shift up or down based on engines rpms

 

ah, I see. Well after having the transmission guys ride with me yesterday, i feel confident that the transmission is not the problem.

Thanks for the clarification!

 

I'm glad you brought this up. I never thought about that when figuring mileage. I personally run 315/75/16 witch are about 34.5 inches tall compared to your 35's. With using your 12% I could inflate my mpg.

Formula: (mileage*1.12)/gallons=mpg

Never have figured mpg on my Ex as I never really wanted to know how bad it is. I need to start for my sell or keep debate.

 

You could try one more thing. I have replaced the 02 sensor and gotten better mileage in other vehicles. Pretty cheap and probably due anyway.

 

34.5inch tires and if you happen to have the 3.73 geared diffs would explain the 10mpg range actauly can find your gear ration on your A pillar sticker 31 or c1 would be 3.73 gearing

 

I just looked at my door sticker and yes, under AZLE it says "C1".

Being a fake car guy, I don't really know what that means. 3.73 ?? Could you please explain what that means and what other options would be?

Also, what is it about the combination of my tires and the 3.73 that gets me 10 vs 12-13?

thanks so much

 

I have been thinking about that.

Funny thing, before the engine went full on TU, I got a code for the bank 1 sensor 2 O2. I changed this and the truck ran like a dream for a week. Then transmission went to hell and the head gasket issue exploded.

I did notice that when I took off the heads a lot of coolant fell into the exhaust Y pipe as I neglected to drain the block first. When I got the Excursion up and running it smoked and hissed like a mother for over an hour as it burned off the excess liquid that was in the exhaust.

Is there any chance that this messed up my new O2 sensor? The bank 2 O2 sensor is the one that was there when I purcesed it 18 months ago. No idea how old it is. If they were bad would I get a code? Or does it have to be REALLY bad?

I guess I could replace both of them.

thanks for the suggestion

 

So, my tires throw off my odometer? How does that work? Do I need to multiple my miles by 1.02?