Mechanics

CRUISE SPEED SURGES

1993 Ford F-150 • 77,000 miles

When set the cruise control the speed surges up and down. I have replaced speed sensor in rear end & checked the ring in the rearened. The speedometer has been replaced and no change. I unplugged the controller behind the glovebox and the cruise works fine. However my ford dealer mechanic says it's no guarantee that is the problem. Also I have replaced vaccine lines under the hood. Please help, Thank You.

Bob m
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Bmiller3316
October 7, 2011.




Check your throttle linkage and cruise cable for binding, if that isn't doing that it may be your servo going bad.

Hmac300
Oct 7, 2011.
Thanks for the info. I checked the linkage and it is not binding. I can't figure why it works fine with the abs controller unplugged. Driving me crazy! Thanks for any & all help.
Bob

Tiny
Bmiller3316
Oct 7, 2011.
Had you said something earlier about eh abs you might get a better response. The abs has the cruise control connected directly to it. As you apply the brakes it kills the cruise. So it's eiteh rgot a short in it or one of the wires are touching where they aren't supposed to an dkilling the cruise. It also connects to the trailerbrake if you have one as well as the speed sensor to the rear. If any of htosea re screwing up or the abs unit itself then your cruise isn't going to work right. Nexttiem give ALL the information you can, engine/trans 4wd or not as well as a complete detail of what is going on.

Hmac300
Oct 7, 2011.
This makes so much sense, I'll check this wiring. I do have trailerbrakes also. Truck is a 93 f150 with a 351w which has the upgrade to the lighting mass air flow kit from ford. Thanks for so much
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Tiny
Bmiller3316
Oct 7, 2011.
He is correct. Check the wiring (especially the trailer wiring) for damage. There also is a plug at the rear of the vehicle for the wiring to the trailer. Check it for damage.

Thanks

Going for test drive Sunday.

Tiny
Bmiller3316
Oct 9, 2011.
Let us know what you find.

I sure will. I have completely unhooked all the trailer brake wiring. Thanks

Tiny
Bmiller3316
Oct 9, 2011.
Thanks

Well it looks like the trailer brake controller is causing the up & down when on cruise. The wiring harness checks out fine also. Thanks for all the help.

Tiny
Bmiller3316
Oct 10, 2011.

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