Nathan Plemons

Well everything has been going too well with the car lately, it's about time something broke. On my way in to work this morning I noticed that my cruise control doesn't work anymore :smash:

I'm not 100% sure when the last time I tried to use it was but I know for a fact it has always worked perfectly. When I get home I'm going to check the very basics and make sure that the throttle linkage is actually still connected to the cruise servo. I was cleaning under the hood the other day and although I really didn't think I was anywhere near there I guess everything is possible.

I guess it could be a vacuum problem but the car does not exhibit any of the symptoms of a vacuum issue. All the heat / AC controls work and it idles just fine. I thought it could be a fuse but all the other stuff that is supposed to be on that same fuse works fine as well.

How should I begin troubleshooting this? I don't have my factory service manuals with me here :(

FSTRNU

When mine stopped working I had a vacuum connection come lose so I bet that is all you have wrong.

TIMSPEED

What exactly is it doing/not doing? Does it work at ALL? For some reason, my cc doesn't accelerate when I try to set my cruise speed up faster. it'll just kick down and start to go, but as soon as I let off the switch, the mph just drops back down to my original set speed. I dunno why this is like this, but I really don't mind it, as long as it WORKS when I set it. :crazy:

BADMUDE

Last year, Corvette Magazine had an article about repairing Cruise control on C4s....I will look to see if I can find it and tell you which one it was in...

_freakmonkeydogboy_

I'm very interested in this topic as well, my CC hasn't worked since i got the car over a year ago, however i have never really bothered messing with it... :D

TealBlueEyes

When my cruise stopped working (and I mean completely, not a loss of a single function), it turned out to be a cracked vacuum line near the battery. Pull the vacuum line off the servo with the engine running and see if you have vacuum. If not, trace the problem back to the engine intake manifold (pass side under the plastic fuel rail cover) where 2 vacuum hoses originate (one goes to the cruise servo). If it's not this, maybe look for a problem with the quick release switch in the brake pedal or clutch.

Jim

Nathan Plemons

Just to clarify, it does absolutely nothing. It has worked flawlessly for two years and now suddenly it doesn't work at all. I turn it on and press the set button, take my foot off the gas and I start slowing down. I press the resume and nothing happens.

I've always liked the GM cruise and how it works, I know exactly how it's supposed to work, and it's not doing anything. :smash:

I just got home and did a real quick check, the throttle linkage is still good, the vacuum lines are still attached but that doesn't mean they aren't cracked. I'll consult the service manual as well and see what it says.

I can't imagine it being a major problem but there's always SOMETHING broken. Oh well what can I expect for an 11 year old car?

SPD DMN

I will put my vote in for vacuum line. I disconnected mine once and forgot to replace it. There were not really any noticable symptoms of a leak.

DarkHalo

Take a look at the vacuum lines going to it and see if they seem corroded or almost melted looking. Mine did the same thing, just out of the blue stopped working and no other symptoms like a vacuum leak normally exhibits. I replaced the lines and it started working perfectly. Both lines looked really corroded right over the battery. I suspect its acid fumes as it stops right at the edge of the battery. :blueangel:

_freakmonkeydogboy_

can someone post a pic of what these "vacuum lines" look line and where they are on an LT-vette? :D

TealBlueEyes

On the cruise servo, they're two small black plastic hoses that run into the unit. Prolly around .25" diameter. You can also see them on the vacuum canister - that thing that looks like a big plastic ball just in front of the driver's front wheel well.

kittmaster

UM........silly question .......did you check the fuse?

Nathan Plemons

Well I found the problem. I figured the first thing to do would be to check the vacuum stuff. One vacuum line runs to the brake pedal, it hols vacuum until I press the pedal and it releases instantly. The other line going to the servo won't hold any vacuum at all. I ran this line down to the other side of the intake where I find a vacuum check valve. I'll post a pic in a little while but in any case it's a combined check valve and T. The T end of it is hard plastic and has become brittle, one end of it had broken.

In the process of trying to remove the check valve I broke off the other end of the T so if figured it's time to replace that piece. A trip to my local parts store was disappointing as usual. Of course they don't have the exact piece that I need but they did have a check valve and a T so I was able to make what I needed. $7 and I'm back in business.