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Discussion Starter #1
Ok guys I have a 97 f250 7.3 with 143k fairly stock. I changed my fuel filter the other day. Now I’m running 2500rpm at 60mph where I use to run 60 at 2000rpm motor doesn’t sound strained. But does seem to lack power on low end. If I run 70 it’s almost up to 3000 rpm. What have I messed up here. I am running a wix fuel filter should I go back to motorcraft. Please help.
 

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I'm assuming its an automatic? Is OverDrive off for some reason? Cheers!
 

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Discussion Starter #3
Yes it is automatic and 4x4. It seems to be going into overdrive cause if I shut it off it downshifts normal. Is it possible for the tach to be reading incorrectly. I have considered changing my fuel filter to a motorcraft filter. Cause for whatever reason I noticed this after changing my fuel filter. I currently have a wix filter in. Also wonder if my torque converter isn’t trying to slip while in overdrive. I checked my trans fluid it looks like it wouldn’t hurt to change it either. Any help is greatly appreciated
 

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Get the codes read. The places that read codes free CANNOT read the codes that are probably stored in your computer. You need either a Forscan, or a good independent shop, or a Ford dealer to read these.
 

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Discussion Starter #6
Anyways like I said I don’t have any check engine lights on. Today I serviced the trans and drained the TC also. Took it for a drive still the same it shifts a little smoother with the new fluid.

Could it be sucking air from where I just changed my fuel filter. I know some guys report having problems with the one piece wix style filter instead of using motorcraft anyways. Next week I’ll change my fuel filter out to motorcraft just to be sure it’s not the issue.

Also when I get up to 70 it’s running about 2800rpm not quite 3000 like I previously stated. Seems to be shifting smooth.

Is it possible my tach is took a crap. And reading wrong.
 

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Can the transmission have codes stored without the CEL on cause at the moment it’s not on.
Only a few transmission codes will light the CEL. Most transmission codes will not light the CEL.
 

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Can the transmission have codes stored without the CEL on...
Yes.
Could it be sucking air from where I just changed my fuel filter.
Anything's possible, but that would have no effect on RPMs.
Is it possible my tach is took a crap. And reading wrong.
Possible - not likely. To find out, use your phone GPS (Google Maps/Navigation) to get the actual speed, and back-calculate the RPM using the tires' RevsPerMile, the rear axle ration (RAR), & the transmission ratio (1:1 if in D; or the O/D ratio from this caption):


(phone app link)


If it's slightly off from the tach, the most-likely reason is that the TCC is not in lockup.


(phone app link)


This caption explains how to calibrate the PSOM:


(phone app link)
 

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Discussion Starter #9
So I’m pretty sure my transmission isn’t the problem. After flushing the trans I found my third brake light was also out. I fixed it also. Then yesterday morning on my way to work the tach started working normal again however today while driving it was still normal. I watched it when it messed up again. I was driving down the highway at 70 and it was reading about 2250 roughly. It suddenly jumped to bout 2800. I’ve checked to see it’s shifting through all the gears and if I hold a steady speed and tap the brakes u can feel the tc disengage then re engage. Is there a sensor I could check under the hood or how do I trace the wires to see if I’ve got a bad connection somewhere
 

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Discussion Starter #10
Ok so I tried to get some videos this morning. Right after I recorded the first one it started acting right so I recorded it also. However I can’t figure out how to post a video
 

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Discussion Starter #13
Ok guys so I’ve got a intermittent problem. It’s back again. From what I’m gathering it’s do to my torque converter not locking in fully or at all. Truck seems to shift fine and all brake lights work but if I tap brakes while at steady highway speed nothing happens. However I have to trailer plug connectors and just noticed one of them is not working properly. Could that be causing my problems. A short or ground in my trailer wiring. On my truck.
 

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Discussion Starter #14
Found my problem I pulled my 7 way plug connector in my bed. I found a wire for that rubbed against the bed and cut the wire and had corroded. It was grounding against the bed. Cut it off and wrapped it with rape to keep wires from touching. Guess I’m rewiring my plug this weekend. Truck shifts better than has in awhile.
 

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Always nice to figure out the problem! Thanks for posting the follow-up. Cheers!
 

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Discussion Starter #16
Yea im pretty certain I’ve found the problem it’s done it a few more times but it may still be shorted up where it was spliced. I’m sure that plug was installed over 20 years ago when it was new. Figure I’ll redo the whole thing to make sure it’s connected and wired right and no more surprises hiding.
 
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