Cruise control problem Intermittent

Mike Combs

Registered User
My cruise control works, but cuts out.
When I hold the ACCEL button the car accelerates and then slows down, over and over until I finally reach my cruising speed. It also has trouble at high throttle requirements. It isn't able to keep speed up hills unless I help it with a little throttle.

There are only a few components in the cruise control system and I have no problem replacing parts until get the right one. Where should I start? Vacuum modulator, cruise buttons, cruise cable, cruise brain???????

Please help.
 
cruise control

I'm about to have my mechanic look at mine, it doesn't work at all. Is there a common failing of the cruise, another words, a good place to start looking? Thanks for any help.
Ed
 
You may have a vacuum leak or a bad vacuum canister.

Keep an eye on the boost gauge when you hit the accel button. If it get near or into boost when it starts slowing down you probably have small leak that's bleeding down the vacuum so the vacuum motor can't hold the throttle open. As soon as the throttle closes, vacuum builds and the throttle opens again and the process repeats. It will try to scan the diagram for the cruise system and post it.

Aaron
 
That sounds good because I had the same thoughts. The only problem with checking the vacuum leak is that I don't have an SC, it is an LX without a vacuum/boost gauge. Where is the leak isolated to in the system? Is it jus the canister and the hose that routes from the brake booster, or can it be anywhere on the engine?? Keep in mind that the brakes work great. So I assume the leak is isolated to the Cruise hose????
 
Mike

I have the factory manual set for the 89 bird/cat, so depending on your year it will cover you.

I looked over the EVTM last night (sorry I forgot to bring it in so I can't scan anything until tonight). The vacuum servo has two valves according to the diagram, one to increase vacuum and one to release vacuum. It also has a safety valve at the brake to dump vacuum if you hit the brakes.

Have you checked all of your vacuum lines and done a leak check with propane/carb cleaner?

Have you checked the safety vacuum dump valve on the brake pedal? If it is adjusted wrong you may be leaking there which would cause your problem.

I will scan the diagrams tonight if possible (2 kids, 2 and 4 yrs).

Aaron
 
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vacuum

I don't have a vacuum problem, the cruise just doesn't work. Any other suggestions would be welcome, as I say I'm going to give it to a mechanic and I hate to pay a lot of diagnostic time if I don't have to. Thanks again,
Ed
 
Don't worry about the scan for me, but you the other guy may need it. I have a thick manual that most likely is the same thing you have.

You have been very helpful. This weekend I am going to go to town on my Cruise. I'm not stopping until I find the reason why it is malfunctioning.

Thanks AGain!
 
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