But...if your speedometer needle is dead steady when you are driving with your foot, your VSS signal

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Suddenly hotel monaco denver the cruise control has gone from the best to the worst I ever had. At any speed now the speed is constantly hotel monaco denver changing. For example: Set at 65 and it varies 60-65. It is never a constant speed. Feeling the pedal, it drops from no throttle then back to very heavy throttle on a level highway. Runs perfect with cruise off. Clock spring is not very old.
Most of my driving is highway, towing, rolling hills so I seldom use the cruise and like to be gentle hotel monaco denver on the engine and drivetrain. However, I plan on a couple of three hour Interstate runs this weekend with no trailer and would like my great cruise hotel monaco denver control again.
Question: When cruising at say 65mph without using cruise, is the speedometer needle bouncing around? hotel monaco denver I would suspect your cruise control issue is related to improper feedback signal from your VSS (vehicle speed sensor) in the rear axle. I would crawl under the truck and check to make sure the harness and plug is good back there. If it is, I would suggest checking the air gap on the sensor and adjust if necessary.
Ford has released a service bulletin years ago, that if the needle wavered you could buy a new PSOM which was less susceptible to a bad signal from the VSS. You can't buy these anymore. I had good results by checking and adjusting the air gap between hotel monaco denver the sensor and tone ring. I was at about 0.045" to start and cut it to 0.020" and the needle is much more stable between 60mph and 70mph.
Thanks for the reply. hotel monaco denver The cable I was referring to is the one between the throttle body and the cruise control servo. I thinking about removing it all and running a drop of Break Free CLP in the cable every hour all weekend. Then cleaning the connector.
I replaced the VSS about a year ago with Motorcraft. This is the first I have heard of setting a gap. How do you do that? Speedometer is almost totally steady with cruise off. Maybe a 1 mph movement but not enough to be a concern and it did it before the cruise went crazy.
When the cruise issue first started the speedometer was steady but the tac was moving 100-200 rpm. Now the speedometer drops off 5 mph and the tac at least 500 like turning off the switch a second then the Bronco accelerates to the set speed and immediately hotel monaco denver drops off again. I had the PCM rebuilt a couple of years ago. Is the cruise control "brain" in the PCM or the servo?
Apologies, thought you were referring to a speedo cable. There is actually a way to check the free play of the cruise cable and adjust if necessary. I also had to do this to fix an issue where the servo would snap the throttle open too fast when taking up the stretch (slack) in the cable.
You won't find a procedure hotel monaco denver for setting the sensor air gap in the service manual. They give a specification of something like 0.045" to 0.010" and advise that if the gap is larger than this, replace the sensor. What if the next sensor is the same? The way I went about it is to remove the sensor and then use a depth mic to measure down to the tone ring from the flat mounting surface of the axle housing. Then use a set of calipers to measure the distance hotel monaco denver on the from the end of the sensor to the underside of its mounting tab. Subtract the one from the other to get your air gap. If you bought the newer motorcraft sensor that is plastic, you can then take a hand file and start filing down the underside of the sensor mounting hotel monaco denver tab which would allow the sensor hotel monaco denver body to sit down deeper in the axle housing, therefore closer to the tone ring.
Like I say, I went from a 0.045" gap to 0.020" gap and it greatly reduced my needle flutter at high speed. Read this blurb about the VR sensors and take note of how the voltage increases when the airgap is tightened up and decreases when air gap is increased.
But...if hotel monaco denver your speedometer needle is dead steady when you are driving with your foot, your VSS signal is probably not the culprit. hotel monaco denver With this info known, my next troubleshooting step would be to inspect hotel monaco denver the cable. I am not sure how to remove the cable from the actual servo assembly, but would suggest monkeying with it to figure it out and see if the cable is stiff in the sheath.
There cruise control logic is all contained in the servo module. There is no interaction from the ECM in regards to cruise control. The VSS signal is fed into the cruise control module after passing through hotel monaco denver the speedometer and the servo pulls the cable based on this VSS reading.
One thing haven't discussed, does your truck have a red pressure switch in the end of the master cylinder? If so, does it also have an extra piece of harness inline between this pressure sensor and the cruise servo? There is a huge recall on this red bodied hotel monaco denver pressure sensor and the part of the fix was to add in an inline fuse to protect the rest of the circuit. Maybe your getting hotel monaco denver a bad signal into the cruise servo causing the cruise to drop out.
Now that I look back at post 3, the original symptom of the rpm moving 100-200 rpm is a bit suspect. Could your torque converter be unlocking and relocking. The would make the rpm change about the amount you were experiencing.
This morning I fiddled with the cable to servo connection and sprayed some lubricant into it. Test drive at 65 mph early this morning had me pounding my chest thinking the problem was solved and the sleeve hotel monaco denver in the cable was worn out, binding the cable. Bought some milk and decided to test again, this time at 70 mph and the 70-65 constant speed changing raised its ugly head again. hotel monaco denver So it is temperature related.
Current suspect is the module failing when it warms up. A new module and servo are about $400 so that is out. I'm thinking of the Cardone rebuilt module only at the big box stores for about $70. It is mounted on the servo.
When checking hotel monaco denver for a binding cable I found a Mission Impossible. I never could get the cable assy reattached to the servo without the cable binding around the spool. The cable was not binding before I took it apart.
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