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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23821
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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When I am driving at a steady speed of 55, the tac keeps

Customer Question

When I am driving at a steady speed of 55, the tac keeps jumping up about 30 to 500 rpms, and then back down. have had it checked on three computer and they all say there is nothing wrong.
JA: What is the model of your '55 Ford?
Customer: Exposition eiddy bower
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: I have been told it might be throttle postion sensor but last service garage said could not prove that was the problem. I have someone that can do the work for me
JA: Does the vehicle hesitate during acceleration? Or maybe speed up suddenly when you aren't even hitting the gas?
Customer: no It does not speed up and I can maintain a steady speed. just every few seconds or minutes it jumps up and then down, never jumps down beyond 1600 rpm
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 6 months ago.
Category: Ford
Expert:  HDGENE replied 6 months ago.

Hello, and thank you for using Just Answer! My name is***** me a few moments to review your question and Ill do my best to assist you.

Expert:  HDGENE replied 6 months ago.

Hello, what year is this expedition? It only does this cruising at a certain highway speed? How many miles are on the truck?

Customer: replied 6 months ago.
55mph and 184,ooo
Customer: replied 6 months ago.
Problem also happen at speed 45 or lower at times, but I can always maintain steady speed
Expert:  HDGENE replied 6 months ago.

What year is the truck, you have it listed as a 1955

Customer: replied 6 months ago.
No, its not yr 1955. its year 2000
Expert:  HDGENE replied 6 months ago.

Right, that makes a difference when trying to diagnose the possible cause. Other than the tachometer jumping around does the truck feel like it is driving over a washboard road? Is the transmission fluid level full and condition of the fluid bright red and clean or brown to black and smell burnt?

Customer: replied 6 months ago.
No it does not feel like driving over a washboard and the transmission has been fully service a few months ago and fluid level is full last time checked This vehicle is a 2000 exposition and not a truck
Expert:  HDGENE replied 6 months ago.

AN expedition is an suv/truck class. No codes, no odd concerns while driving other than the tach moving, do you feel the engine surge?

Customer: replied 6 months ago.
The engine seems to be running smooth and I can maintain a steady speed and vehicle never slows down
Expert:  HDGENE replied 6 months ago.

Does the concern seem to happen at a shift point? Sorry to ask multiple questions, im looking for something to relate to the tach behavior