Want to replace cruise control servo?

[Mont91]

When I was having odd problems with my cruise switches I took them apart and cleaned them, man were they cruddy inside, works fine now.

 

[jauguston]

Mont,

I don't "think" the issue is with the switches. When I push the set/accelerate button to set the speed when first activating it if I just push the button and let off of the throttle I slow down 5-7 mph before the cruise stabilizes the speed. If I hold the buttom until I feel it taking the pedal away from my foot it will slow down 2-3 mph. It is just a PITA to have to manually speed up to 2-3 mph above what I want to set it. I know, for you guys without cruise are saying, quit your ******** we have to push on the pedal all the time. What can I say-I'm spoiled (-:

Jim

 

[The Warden]

Are there any adjustments that can be made to the cruise system at all? Another thing mine does is when I push the set-accelerate button when the cruise is set in a attempt to raise the set speed it instead goes to a slower set speed.

I have the same issue; I've just learned to live with it. The last time this was discussed (back in the TDS days, and a number of archives ago), many other people reported the same problem...and no one at the time had any idea how to fix it. I think that was actually an electronic issue, as opposed to the diaphragm.

When you say "Replace the servo' what part exactly are you speaking of. Do you mean just the diaphram part or it and all the electrical stuff that goes with it.

To my understanding, there are basically three parts to the cruise system on our trucks (and I presume the vans are set up the same way, but I can't speak with authority since my old E-350 didn't have cruise). The servo is the circular piece that the cable to the IP is attached to; IIRC there's one electrical plug and on or two vacuum hoses going into it. The "amplifier" is the electronic brain box of the unit, and is under the dash. The third part is the switches on the steering wheel.

I think there are also some additional vacuum parts (for example, I think the "Resume" function requires a vacuum reservoir to work), but that's the basic system.

Personally, I'd like to hear more about the all-electrical system that it sounds like later IDIs have. While I know that electrical parts can fail too my experience with M-B vacuum systems tells me that the vacuum portions of the CC setup (the servo, etc.) that we have has a very finite lifespan, and sooner or later, parts for it are going to start getting scarce...especially since it's already a junkyard-only item...

I don't "think" the issue is with the switches. When I push the set/accelerate button to set the speed when first activating it if I just push the button and let off of the throttle I slow down 5-7 mph before the cruise stabilizes the speed. If I hold the buttom until I feel it taking the pedal away from my foot it will slow down 2-3 mph. It is just a PITA to have to manually speed up to 2-3 mph above what I want to set it.

Going back to the same CC discussion I remember from a number of years ago, what you describe is VERY common...and not just with IDI's. A friend of mine used to own an '91 Explorer that acted identical to what you're describing; my truck does the same thing. Someone even stated that his truck had done this since it was new...so, maybe this was a design flaw from the beginning? Ford seems to have fixed it in recent years, though; the Town Cars at work don't do this

The other thing I found is that I have to hold the button for a good 2 to 3 seconds for it to "activate". I have to do this with the ON button as well as the SET button. Again, this seems to be a common thing...maybe everyone's switches are gunked up on the inside, or maybe it was another design issue. I've never seen the underside of an '87-'91 truck cruise/horn pad, but I have yet to figure out how to take apart an '80-'86 cruise/horn pad without ruining it. If anyone has done it, I'd love to hear about how you did it! I'm sure it couldn't hurt...

 

[Agnem]

I'd be happy if mine would just keep the set speed. It holds it a while, then all the of the sudden decides to speed up or slow down. Kills the fuel milage. I've been thinking it's the servo. I'd be interested in more details on the vacuum to all electric conversion.

 

[jauguston]

Warden,

Have you checked to see if ,like mine, when I just push the set button and release it I slow down 5-7 mph. If I hold the set button down after 2-3 seconds it takes the throttle. You may actually be activated but have to slow way down for it to take the throttle.

I thought most of these old cruise controls would increase speed about 2 mph each time you hit accel after the system was in operation.

Jim

 

[The Warden]

Have you checked to see if ,like mine, when I just push the set button and release it I slow down 5-7 mph. If I hold the set button down after 2-3 seconds it takes the throttle. You may actually be activated but have to slow way down for it to take the throttle.

Yes, I have checked. Mine actually slows down 2 to 5 mph...but, if I don't hold the button down for about 2 seconds, it doesn't do anything. This goes for the SET button as well as the ON button. I think I have to hold the SET button for about 5 seconds for it to actually take the throttle.

I thought most of these old cruise controls would increase speed about 2 mph each time you hit accel after the system was in operation.

According to the owner's manual, that's how it's supposed to work. My ACCEL feature has always been quirky, and it seems to depend on vehicle speed. If I press the button at 55 mph, it'll speed up...if I press the button at 65 mph, it instead starts slowing down to about 60, then starts speeding up in an erratic manner. I find it better to just not deal with it. FWIW, the DECEL button works perfectly.

Certainly, the IDI cruise is primitive compared to the ones we see in new cars the setups on the Town Cars at work are FAR smoother, accurate, and reliable. If I didn't loathe g@$ engines so much, I would seriously consider owning a late-model Crown Vic/Marquis/TC...for passenger cars, they really are tanks (guess that's why they're so prevalent in fleets )

 

[James.Taylor012]

I'm missing the cable off my servo can that be replaced or do I need to replace the whole assembly?

 

[79jasper]

Warden, that seems mostly normal.
At least compared to the 460 I drove.
Hold it for a little bit longer and it'll downshift and haul ****.

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