I found this the other day!
Speed Control - Coast And Acceleration Modes - Abnormal Operation In High Ambient Temperatures Article No.
PUBLICATION DATE: February 8, 1989
ISSUE Abnormal speed control operation in the coast and acceleration modes may be caused by loss of electrical contact between the steering wheel slip rings and brush assembly. This condition usually occurs in high ambient temperatures when the steering wheel slip rings and brush assembly are warm.
ACTION Improve the electrical continuity of the steering wheel slip rings and brush assembly by applying a new service released grease on the contact area. Refer to the following procedure for service details.
Remove the steering wheel. Refer to the appropriate Car or Light Truck Shop Manual for service details.
Clean the old grease from the steering slip rings and brush assembly contact areas.
Apply the new service released grease, (E8AZ-19590-A), on the steering wheel slip rings and brush assembly contact surfaces. This new grease can be identified by its bright orange/red color.
Reinstall steering wheel.
PART NUMBER PART NAME CLASS
E8AZ-19590-A Grease B
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Eligible Under Basic Warranty Coverage
OPERATION DESCRIPTION TIME
890304A 0.4 Hr.
BASIC PART NO. CONDITION CODE
OASIS CODES: 2900
The servo in under hood near driver's side hood hinge
I don't have a good pic showing it except for this:
pic by Rock Auto;
This is for an 89 4.9 by Chilton
1.Disconnect the wiring at the servo.
2.Disconnect the adjuster from the accelerator cable.
3.Disconnect the vacuum line at the servo.
4.Remove the actuator cable-to-bracket *****.
5.Remove the pins and nuts retaining the servo to its mounting bracket and lift it out.
6.Installation is the reverse of removal.
1.Snap the molded cable retainer over the accelerator cable end fitting attached, to the throttle ball stud.
2.Remove the adjuster retainer clip, if installed, from the adjuster mounting tab.
3.Insert the speed control actuator cable adjuster mounting tab in the slot provided in the accelerator cable support bracket.
4.Pull the cable through the adjuster until a slight tension is felt without opening the throttle plate.
5.Insert the adjuster cable retainer clip slowly, until engagement is felt, then, push it downwards until it locks in position.