gf261

Was trouble shooting the cruise control and now I am stumped. I removed the multi-pin plug and tested per John Pirtle's procedure. All of the pins do what they should except for the bridging of terminals 3 and 5 and the pushbutton test for 7 and 12. I will do these tomorrow. The problem I am having is that the cruise works, it just won't maintain a speed. It loses about 15-20 mph depending on the hill size and then ever so slowly attempts to catch back up. Cancel works fine, but if you give it just a wee bit of accelerator pedal when it is trying to catch up, it seems to work. My question is, would this be a vacuum leak or something electronic? By the way, the vacuum reservoir holds a vacuum. Go figure???

LI Steve

Garrett - Unfortunately, I don't have the answer, but I do have the exact same problem. I have swapped out the cruise control electronic 'brain' (twice), and my system holds vacuum also. I can set, accelerate, and cancel via the cruise control - no problem. The car just won't maintain speed. Almost seems like it will hold throttle position, but not speed.

Any help would be greatly appreciated!

gf261

Thats mine! It is so aggravating. I am thinking of swapping the brain in my 89 for the 87 and see if it works then. That way at least I would know. I am curious as to whether or not the cable itself could have something to do with it. It has an adjustment on the cable that mounts to the side of the intake, but I hate to fool with that until all else fails. If I figure something out I will let you know. I guess our difference is that mine will not accelerate. Thats what is really crazy. It is also what makes me think that the vacuum may be leaking at some point. It just seems that it is strong enough to set, but not strong enough to accelerate or maintain under the strain of climbing a hill.

Chris

Garrett:
1) You have no or little vaccum, easy to check, unplug the connector heading to the vacuum resorvoir on the drivers side fender, check for hiss ....
2) Cruise servo is not working, check inside drivers side front fender after removing fender liner. See if there is any actuation.
3) Cruise cable stretching ... not sure I put much faith in that one !!

Good luck

Chris

edit : The brain in the 89 is not the same as the 87.

gf261

Chris I unplugged the Y-shaped splitter that runs off the 4-way from the brake booster. I then disconnected the black and white vacuum lines and checked them independantly with my Mityvac and they both held vacuum. Do you have a way to check the servo? Fender liner is still out. The cable deal was more of a "its getting dark, the mosquitos are awful and I just drank my last Michelob" kind of guess!

Chris

No I don't but its a pretty simple device.

If its not actuating as pet of the test you are getting real close. I'd check the elctrical connector 1st to see if corroded or something.

Chris

AO

Guys-
I had this exact same problem. It continued to get worse (the decelleration) to the point where it seems like it wasn't even on. Accel still worked though. After much aggrevation, I decided to resolder all the points on the brain's curcuit board as others have had success with that. Took about 2 hours (and I'd never done this kind of work before). Works like a champ now! Mostly I just touched the soldering iron to the points ont he board and remelted the solder. A few timems I had to actually add new solder because the old stuff evaporated. One of the most simple/satisfying repairs I've made in a long while.

Thaddeus

Here's a really dumb question...

Where's the cruise actuator located? I haven't seen a box anywhere under the hood... I do have a switch for it... the one time I tried to use cruise, I was afflicted with bad vacuum leaks so it wouldn't work in any event. Hasn't been a high priority before now but I'd like to get it working, if it exists on my car at all..

WallyP

The tempostat is located behind the fender liner behind the driver's side front wheel - on LHD cars, at least!

AO

But the brain is located behind the radio. You can access it from the pass side. If you take off the pass side center console cover (pass tray too), you'll see a silver box about the 4x6x1 located near the firewall. This is the cruise brain. It's bit hard to wiggle out, but it can be done. Then it simply unplugs from the harness. Bend up the tabs on the box and the circuit board slides right out.