When I turn on the cruise control, my FC4S speeds up and slows down and doesn't seem to stabilize. What might be wrong? the controller? Is this another grounding problem?

 

Non turbo serires four????? How about the vacuum line leaking to the actuator or the cable being waaaaay loose and needs some tightening up?

I read what you wrote and come up with the cruise control engaging, and staying engaged but not maintaining a steady speed.

 

Endurance to me usually means how long I can go without peeing.. and yes.. it engages but fails to maintain cruise speed.

 

Then look for or get another vacuum hose and make sure it's going to the right place. And make sure there is not a bunch of slack in the cruise cable and that it is not in a bind or chaffing something. It's very doubtful the cruise control unit itself is at fault nor the switch on the dash.

The cruise uses the tach signal to maintain speed if the above parts are working. So if your tach is doing *funny* things, then that is a possible culprit. As in the needle sticking, pausing, jumping up/down.

I'd look for the vacc and cable first.

 

Tach works just fine. I tried looking for the cruise control cable, but cant find it. Haynes doesn't have it in their manual. I'm going to look for it in the factory service manual. From what its doing, it seems like the cable is doing funny things. WD-40 time, me thinks. First job is to find the damn thing, though. You might be on to something with the vacuum hose. If not the cable, its got to be the hose. Thanks for all the help!

 

Found the cc cable in the factory service manual. Found it on the car and sure enough, it had a lot of free-play. I tightened some nuts at the actuator/control unit (that cylinder in front of the cold-climate start assist reservoir and behind the charcoal canister) and the cable now has no slack. I am not going to test it till I get my fuel leak fixed. Anyone think this might NOT be the fix??

 

Just a little caution. You don't want the cable dead tight nor loosy goosy. Dead tight and the idle rpms will be effected. You should be able to touch the INNER cable lightly and the throttle lever should not move.

But you don't want it loosy goosy because when you engage the cruise the thing won't be very responsive and give symptoms like you describe.

Inspect the vacuum line going to the actuator at both ends and make sure it isn't cracked/leaking.

 

Yep. Vacuum line is fine. Now, unless the actuator is conked, it should work. I have the C.C. cable set up to where it is not moving the throttle lever with a little push on the said cable. I think I have it just right. I will verify this soon as I make sure my engine won't catch on fire in the process because of the leak discussed in other topics (Yes, it is the damn P.D).

 

Cruise control works very well now. Thanks for all the suggestions. It was the slack in the cable, afterall.