I have a 1987 F-150 Lariat XLT; 5.0 engine, fuel injection.

I'm having problems with the cruise control; when I first engage it it accelerates hard, then it "hunts" or surges to maintain a set speed. I've looked for info in some aftermarket service manuals,ie Chilton without success. The last time I called Helm about factory manuals I was told that they were out of print.
Has anyone experienced this problem or, know where I can start to troubleshoot it. Any help will be much appreciated.
Thanks in advance,
Steve

 

If I recall, your cruise control is governed my the speedo cable, and you have a two part speedo cable... a run from the transmission to a black circular device (which is the speed sensor part of the cruise) and then from the speed sensor to your speedometer.

I'd look in a few places. First check for slack in the chain between the cruise control dash pot and throttle. Second, make sure there are no vacuum leaks in the dashpot itself, or in the lines that supply vacuum. Finally, lubricate the speedo cable. It might be sticking, winding up like a spring, then releasing, causing erroneous output... although if this were happening, I would expect that you would see your speedometer needle jumping about.

 

there is no 2piece speedo cable, the vss is mounted in the tranny and the cable comes out of that. But anyway, you need to put a servo on it, the potentiometer part of the servo that gives the amplifier feedback as to the position of the cable must have a dead spot worn into it, I see it all the time.

 

Thank you, that gives me a good idea where to look, I'll let you know what I discover. Steve

 

Just an FYI about the factory service manuals... I see them for sale on CD-Rom on Ebay all the time for less than $15 usually.

Usually about once a month they pop up.

-Joe-