I am having a wierd problem with my 94. Sometimes, the cruise does not disengage when I push the brake pedal and/or slowly accelerates past the "set" point for no apparent reason. Blipping the throttle pedal disengages the problem temporarily, but then it often reaccelerates, from any speeed, even when I turn off the cruise control switch. I am thinking that the vent servo may be sticking closed causing constant vacuum on the diaphragm - any other thoughts? Easy ways to check?

In addition, the A/C compressor clutch sometimes fails to engage. If I lift the hood and tap the front of the clutch, it immediately engages, and all is good. Not sure that the two problems are related - but they usually seem to occur simultaneously.

I would appreciate any help from those who have seen and fixed similar problems. Thanks, Rich

 

Remove both.

 

This is an extract from a post I wrote but for a different problem though. I have changed it to be applied to your problem. Check this post out, its not your problem but some of the information might be beneficial.
http://forums.corvetteforum.com/c4-t...-question.html


You need to ascertain first if the servo relays are getting any voltage. This needs to be checked while driving the car. You will need 2 DVMs and two 5 foot lengths of wire.

You need to make 2 connections with 2 pins on the servo connector. Take nothing apart. Shove in a straight pin, hard piece of wire or anything that will make contact thru the back side of the connector. You will be connecting one wire each to pin E (vacuum valve), and the other to pin A (vent valve) (opposite ends of connector). Run the two wires inside the car and connect one wire the each + input of each meter. Ground the negatives to metal inside the car. Keep track of which meter goes to what pin.

(IGNITION KEY OFF) To verify you actually have contact with the pin, turn each meter to read resistance. This will measure the resistance thru each relay and should measure about 45 ohms. Once verified, change back to voltage.

Normal Circuit operation, Driving car.
When you engage the cruise (set switch), voltage is applied to pin E (vacuum valve) for about 1 second then released. This brings vacuum into the system. SIMULTANEOUSLY, voltage is supplied to pin A (vent valve) and closes the system to hold the vacuum. Pin A will stay up at 12 volts and pin E will be 0 volts.

This is what basically happens the first few seconds. The cruise module momentarily opens and closes the relays to adjust the speed, but this is the basic steady state configuration. If car is to fast, it will open (pulse) the vent valve. If to slow it will open (pulse) the vacuum valve adding vacuum. This servo process happens very quickly while maintaining speed. Hence it adjusts the vacuum motor.


What you need to find out is if the you are getting voltage to pin E or A when cruise is turned off. If the vent valve relay is not held on, then the system cannot hold vacuum for the motor in the servo. Find out of you are getting any voltage to either relay when the system is off. In addition, the brake pedal vacuum vent switch should vent the system thus disengaging the servo motor.

First find out if you have any electrical stimulus problem from the cruse module, if not, then you can target in on the vacuum and servo part of it.

 

Thanks for the info - I will start there. It sounds like my problem is the inverse of most folks - my cruise accelerates, and does not want to cut out unless I pulse the throttle (brake has no impact), maybe giving the vacuum system/servo a jolt. I recall the start of a thread a few months ago with this problem - but can not find it now. I think that it was something like "my car tried to kill me"!