Cruise Control Jerky

[jimboesfo]

When using the cruise control, the truck will jerk/lurch when the engine is not under load, i.e. going down hill. The truck does not exhibit this jerk/lurch when the cruise control is disconnected. At first I thought that maybe there was a vacumn leak, but I understand that the cruise control on the 97 is electronic. There is no indication anomaly when this occurs, the cruise control light remains illuminated. I searched the forum for similar problems with no luck. Any ideas?

 

[mitchevans]

its your brakes engaging. when you go downhill the cruise tells the brakes to engage enough to maintain your set speed. ( thats what the jerk is.)

at least thats what i think on the subject

 

[MustangP51]

I don't think the cruise control has any control of the brakes.


Is your gas pedal sticky, or difficult to move? The throttle body might be dirty and making it hard for the computer to make fine adjustments to throttle valve.

 

[mitchevans]

I don't think the cruise control has any control of the brakes.


Is your gas pedal sticky, or difficult to move? The throttle body might be dirty and making it hard for the computer to make fine adjustments to throttle valve.

in my old pontiac grand am, when i was going downhill it would tap the brakes to keep me going the designated speed.

but then that pontiac had alot of problems...

 

[MustangP51]

I'm almost positive that the Explorer's cruise control does not use the brakes. I think the system will just disengage if the speed increases/decreases a certain amount over the set speed.

I think that only recently that cruise control systems are starting to control the brakes with whats called "Adaptive Cruise Control" but no Ford has that yet.

 

[jimboesfo]

I don't think the cruise control has any control of the brakes.


Is your gas pedal sticky, or difficult to move? The throttle body might be dirty and making it hard for the computer to make fine adjustments to throttle valve.

It's definitely not the brakes being applied.

The gas pedal is not sticky or difficult to move. When the cruise control is off, the truck is very smooth while maintaining speed going down hill. It does feel like the cruise control is not providing a smooth input to the throttle. I can't understand why it would only occur during downhill operation with cruise control.

 

[MustangP51]

Try cleaning the throttle body. It cant hurt, and its the cheapest thing to start with. Buy a can of throttle body cleaner ( do not use carb cleaner) and a toothbrush and scrub down the throat and the throttle valve. when its clean spray a little WD-40 on the valves pivot points. Other than that I really don't know what else it could be.

 

[gijoecam]

Ditto. I can guarantee it's not the brakes. I'd be surprised if a GrandAm applied the brakes too. That type of braking control system didn't come online until the last few years.