Cruise control problem - 85 El Camino (LG4)
 

My cruise died a quick death. I replaced the vacuum servo with a rebuilt, but it tried to work then died again. It'll go close to full throttle, back off, then just disconnect. Also, my Torque converter wouldn't lock up at the normal speed.

This is the second rebuilt vacuum servo(first was back about 18 months ago).

Could this be a bad servo or could I be having other problems such as VSS, buffer, or the cruise module (brains) itself.

Many thanks!!!

Check the brake pedal operated switches - they control cruise unlock, TCC power, in adition to the brake lights.

Tim

Thanks for the quick reply, Tim.

Yes, the brake pedal switches are good. My SES is not setting any codes, i.e., no Code 24.

Because of this can I assume my VSS and buffer are good? Is there a way to test the cruise control module, then the vacuum servo?

Thanks!

Is the vacuum check valve between the manifold & the vacuum reservoir functional? Is the vacuum release valve, or the hose connecting it to the servo leaking when the brake is not depressed? In other words, will the reservoir hold a vacuum for quite some time, after the engine is shut off?

If the vacuum supply is OK, start by checking all of the inputs from the control switchs & the speed buffer (power, ground, set, accel, brake detect, speed buffer input) at the cruise module - make sure thay are not intermittant. The speed buffer may have two separate outputs - one for the ECM & speedo & another for the cruise module.


Tim