Cruise Control

[MacDaddy]

Hi, I have an 88 also, with alittle different Cruise control problem. Cruise will engage but will disengage after a short while, espcially when I take a hill, even a small one. Could this be the mentioned vacum line? Thanks and God bless :blink:

 

[Seabronc]

It may not be that particular line, but it definitely sounds like a vacuum problem. The vacuum is supplied directly from the intake manifold. Put a vacuum gauge on it and see what the vacuum reading is under load. You could rig a temporary setup by using a long piece of hose to a test gauge inside the cab to monitor the vacuum under different conditions. Check the condition of the hoses, could be cracks in one or more.

Good luck,

>-

 

[MacDaddy]

It may not be that particular line, but it definitely sounds like a vacuum problem. The vacuum is supplied directly from the intake manifold. Put a vacuum gauge on it and see what the vacuum reading is under load. You could rig a temporary setup by using a long piece of hose to a test gauge inside the cab to monitor the vacuum under different conditions. Check the condition of the hoses, could be cracks in one or more.

Good luck,

Thanks Seabronc, I'll give a look and vac test. Let you know what I find.

 

[miesk5]

yo,

You got da skinny from my pal Seabronc, so I'll just incl this for others to use and you too in case of any future CC issues;

Cruise (Speed) Control (Vacuum) "TRICKS OF THE TRADE" Troubleshooting TSB 90-25-12 by Ford for 86-91 Bronco, Aerostar, Econoline, Explorer, F-150, F-250, F-350, Ranger & cars Source: by Ford via miesk5 at Miesk5's Home Page of Big Bronco Links home.comcast.net

Significant Excerpts;

"...Speed drops of more than 1 or 2 mph may occur while in speed control operation on grades or under other load conditions. This is especially true on vehicles that are equipped with automatic overdrive transmissions or with manual 5 speed transmissions. These speed drops are due to limited engine power available in the overdrive (or the highest gear of a manual transmission) mode of operation. Under heavy load conditions, such as hilly or mountainous areas or during trailer tow, the vehicle speed may drop even more. When speed drops of 10 - 13 mph (16 - 21 km/h) occur the speed control system will, by design, automatically disengage.

Visual inspection is an important part of diagnosis. The visual inspection should be done to locate obvious reason for the customer concern.

When performing visual inspection, check all items for abnormal conditions. Look for items such as bare, broken or disconnected wires and damaged vacuum hoses.

For the speed control to function properly, it is necessary that the speedometer cables, if so equipped, be properly routed and securely attached. All vacuum hoses must be securely attached and routed with no sharp bends or kinks. The servo (throttle actuator) and throttle linkage should operate freely and smoothly

If speed control performance is poor on moderate grades, the adjustment of the Bowden cable/bead chain should be checked and readjusted if necessary. The automatic transmission shift linkage should also be checked for proper adjustment.