Cruise control changing speed by itself

[Silvermarten]

Hi all.
Newbie here

I've a 1993 Taurus station wagon . Approx 140,000 miles . Automatic .

Recently when in cruise control it has started speeding up and slowing down quite noticably . This is when we are on flat level highway .
Will go from 65 mph to 75 mph , then back to 65 , then up to 75 etc, etc .
I've quit using the cruise control for safety .

Any suggestions on what I need to look into to find out what is causing this ?
Thanks.

[shorod]

See if the plastic/nylon throttle deal is stretched or stressed. Also, you could have a servo that has a leak in the diaphragm. I don't recall if the '93 has a vacuum or purely electronic servo....

-Rod

[Silvermarten]

Originally Posted by shorod

See if the plastic/nylon throttle deal is stretched or stressed. Also, you could have a servo that has a leak in the diaphragm. I don't recall if the '93 has a vacuum or purely electronic servo....

-Rod

Thanks Rod.
Have a Haynes repair manual , it mentions vacuum hoses so I'll check into that .
No reference to a servo ( but maybe I'm looking on the wrong pages ) .
I'm a novice car repairer so it'll be a slow project
Thanks for sharing your thoughts.
I'll let you know how things go .

[tripletdaddy]

You have a vacuum servo. Just follow the two parallel cables that attach at the throttle, one will go through the firewall to the pedal and the other to a plastic and metal canister with rubber vac lines on and to it. I think 95 was the last year of the vac servo on the Taurus. While looking at the two throttle cables, check at the end of the cruise cable at the throttle connection for anything that looks like it is hanging up, boogered up, etc. I've seen some arrangements where the cable sheath and cable end cover catch because something went out of place, holding the throttle open enough to race the engine and scare the driver!

[Silvermarten]

Originally Posted by tripletdaddy

You have a vacuum servo. Just follow the two parallel cables that attach at the throttle, one will go through the firewall to the pedal and the other to a plastic and metal canister with rubber vac lines on and to it. I think 95 was the last year of the vac servo on the Taurus. While looking at the two throttle cables, check at the end of the cruise cable at the throttle connection for anything that looks like it is hanging up, boogered up, etc. I've seen some arrangements where the cable sheath and cable end cover catch because something went out of place, holding the throttle open enough to race the engine and scare the driver!

Thanks
It *appears* to be something with the servo . The cables seem free and smooth but when moving the gas pedal ( not running ) there is something that binds and releases inside the servo .

Is this something a novice auto repairer is safe to remove and replace ?
Just concerned as the Haynes manual says to take the car in to have cruise control worked on.

Thanks again. You guys are the best !!!!

[shorod]

Hmmm, that seems a bit odd. Typically the cable for the servo won't move when just operating the throttle. You may want to inspect the linkage at the throttle plate a bit more and see why the cable for the servo is moving when you operate the throttle with the pedal.

-Rod

[Silvermarten]

Originally Posted by shorod

Hmmm, that seems a bit odd. Typically the cable for the servo won't move when just operating the throttle. You may want to inspect the linkage at the throttle plate a bit more and see why the cable for the servo is moving when you operate the throttle with the pedal.

-Rod

Hmmm .......... I'll do a double check and see what is/isn't moving . I didn't see the cable move but there was a very clear sound and feel of 'something' binding & releasing in the servo.

On the plus side , it may be fixed . I moved all the cables/linkages around while searching for signs of binding as suggested . Saw nothing obvious but I went ahead and tried cruise control several times today while going to/from work . It worked GREAT every time No wild 'n scarey speed changes .

Thanks for all the help !!!!