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Cruise Control Fix

Discussion in 'The Garage' started by wadinator, Sep 9, 2003.

  1. wadinator

    wadinator 1/2 ton status

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    I'm trying to find online references about how the cruise control system works in my 87 Chevy /forums/images/graemlins/burb.gif and I'm not having much luck. I'd like to learn how they work, how to diagnose problems with them, and how to adjust/fix them.

    Can someone please point me in the right direction? Thanks!/forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/usaflag.gif /forums/images/graemlins/ears.gif
     
  2. sapper

    sapper 1/2 ton status GMOTM Winner

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    its probablly the linkage broke or the servo has a hole in it, look on the drivers side of the carb/tbi, there should be a linkage running from it to the servo mounted on the fire wall, the servo depending on what year is a round black rubber thing that when the cc is on takes vacum and holds the linkage in place to keep the speed steady, if its still hooked up and no holes i dont know what you need to do after that
     
  3. wadinator

    wadinator 1/2 ton status

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    My cruise isn't "broke". It just doesn't kick down all the time like it should on uphill grades. How do you adjust that?
     
  4. Sidepipes

    Sidepipes 1/2 ton status

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    NO way to adjust that that I know of. It kickdown on throttle position/ engine vacuum, the cruise control has nothing to do with the kickdown.
     
  5. wadinator

    wadinator 1/2 ton status

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    OK, if the cruise has nothing to do with it, explain this to me...

    I'm cruising down a flat stretch of road in my 87 burb with a 350 and a 700r4 tranny. The cruise is set at 60mph and I'm in OD and the torque converter is locked up. Then I begin cruising up a stretch of road that has a slight incline, and my speed starts to decrease. Sometimes it comes out of lockup (seems like a downshift to a unknowing person) and the burb maintains a speed close to 60. But most of the time the damn thing just stays in lock-up and the speed drops till I get sick of driving so slow and so I step on the gas pedal myself. Just slightly stepping on the gas pedal causes the truck to finally get out of lock-up and start picking up speed again. At this point, I can take my foot back off the gas pedal cuz the cruise is still engaged and the truck always returns to the set speed before locking back up again.

    So how the heck to you get the truck to come out of lockup without me having to tap the gas pedal every time I begin ascending a slight grade? It's annoying the bejeepers out of me!
     
  6. MOABDADC22

    MOABDADC22 1/2 ton status

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    [ QUOTE ]
    My cruise isn't "broke". It just doesn't kick down all the time like it should on uphill grades. How do you adjust that?

    [/ QUOTE ]

    My 90 K5 did that too. I had to adjust some of the "slack" out of the cable linkage. Worked like a charm after that. /forums/images/graemlins/thumb.gif
     
  7. wadinator

    wadinator 1/2 ton status

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    [ QUOTE ]
    My 90 K5 did that too. I had to adjust some of the "slack" out of the cable linkage. Worked like a charm after that.

    [/ QUOTE ]

    How do you do that? Details, man. Details! /forums/images/graemlins/ears.gif /forums/images/graemlins/thumb.gif
     
  8. wadinator

    wadinator 1/2 ton status

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    Bump /forums/images/graemlins/thumb.gif /forums/images/graemlins/ears.gif
     
  9. MOABDADC22

    MOABDADC22 1/2 ton status

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    Mine had the little chain (the one that looks like the thing that military dog tags are attached to) I just unhooked on end and took the slack out by moving the chain up a couple of "balls".
     
  10. Sidepipes

    Sidepipes 1/2 ton status

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    The answer is simple, the cruise control is not openning the throttle enough to cause the downshift through the TV cable. The problem is with the TV cable not the cruise control. Try the same hill at the same speed without cruise on and I bet the vehicle will react the same.
     
  11. wadinator

    wadinator 1/2 ton status

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    OK, so it's the TV cable and not the cruise. How do you adjust it? Where is the TV cable located? Is that what I need to adjust?
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    cruise fix

    never looked at a Fiero cruise system, but since you've got "Electric" cruise, the non-DIS information may help you.

    The service or electrical manual covers cruise control shooting quite thoroughly and is pretty easy to follow IIRC. Just don't have my books here.
     
  13. jarheadk5

    jarheadk5 1/2 ton status

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    Think long and hard, and do some searching on the topic (TV cable adjustment) before you go out and mess with the TV cable. It's very easy to go too far in either direction, and the result can be a cooked 700R4, and that's EXPENSIVE.
    For the record, my '87 305/700R4 with cruise will stay at the set speed on flat ground, and will try to keep that speed on uphills. It unlocks the converter, and will downshift to 3rd if it drops too much speed. My cruise won't accelerate though; it'll only maintain a set speed, or coast. I had to make a servo-to-throttle linkage for mine out of coat hangar wire because the OEM linkage was missing.
     
  14. wadinator

    wadinator 1/2 ton status

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    So to get my truck to kick out of lockup while the cruise is set and speed is dropping as I go up a hill, I need to adjust the TV cable?

    Is that the final answer? /forums/images/graemlins/ears.gif
     
  15. Blue85

    Blue85 Troll Premium Member

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    Step back and be logical. If the truck shifts normally when you use your foot on the throttle, then nothing is wrong with the TV. If the problem only occurs while using cruise, then it is a problem with the cruise. I think this thread was on the right track back when it was talking about the cruise control linkage. If that has the slack taken out, then it must be a problem with the servo or controller.

    How is inability to maintain speed while using cruise control a problem with the transmission?
     
  16. wadinator

    wadinator 1/2 ton status

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    [ QUOTE ]
    How is inability to maintain speed while using cruise control a problem with the transmission?

    [/ QUOTE ]

    I don't understand that either! My truck shifts fine when I'm not using the cruise control, it just fails to come out of lockup to adjust for climbing hills when the cruise is set.

    I've noticed that the little rod running from the cruise servo (? that little rubber cruise control thingy about the diameter of a tennis ball) to the TBI is threaded and can be adjusted. Could adjusting this quicken the drop out of lockup?
     
  17. R72K5

    R72K5 Banned

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    usually the switch mounted at brake pedal arm near the stop lamp switch is faulty wornout, theres electrical half and vacuum hose half, check it out and make sure its adjust right, if its not screwed in close enough to the pedal, IE has loosened up and or slipped- then cruise wont work
    also check with engne running that you have vacuum to the servo unit under the hood on fender or wheel tub, this is the unit with the speedo cables connected to it, also check the hoses there make sure they are tihght and check the electrical plugand wires make sure they are not corrodded or loose or damaged either,. check the hoses for cuts or breaks or slits, if the switch at pdeal arm is ok and everything at the servo unit looks good and speedometer registers then check the vacuum accelerator control diapragm mounted ot intake, put vacuum directly to it from engine vacuum source and see that it sucks in and pull the linkage with good travel, if it barely moves anything then it probably is leaking from a cut or etc. probably shoudl check that at the same time that you check for engine vacuum source at the servo and brake pedal switch also,.


    hope you find the culprit, should if you take your time and think /forums/images/graemlins/laugh.gif cruise is kind of a complicated little setup for the novice, have to study it to understand how it cuts in and out and such. basically what happens when you step on brake pedal is that the vacuum hose at the brake switch opens up and removes vacuum source fromt eh diapragm for the acclerator linkage mounted to the intake manifold, vacuum will get sucked through easiest way, and the diapragm is not as easy as a break at the switch at pedal. and the electrical partof the switch tells the servo to not allow more vacuum to go into the dipragm until you hit resume or the button again.,

    none of this has anything to do with the tranny other than that the speedo cable fromt he tranny goes through the servo unit before it goes tot he speedometer, this is only for the servo unit to keep you at the speed you want to go and to moniter that, its like alttle RPM brainbox and they can be faulty after long service time. but they are commonly found and so good used units are simple to find, thrown away billions of cruise setups, too common.
    good luck
     
  18. Sidepipes

    Sidepipes 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    How is inability to maintain speed while using cruise control a problem with the transmission?

    [/ QUOTE ]

    I don't understand that either! My truck shifts fine when I'm not using the cruise control, it just fails to come out of lockup to adjust for climbing hills when the cruise is set.

    I've noticed that the little rod running from the cruise servo (? that little rubber cruise control thingy about the diameter of a tennis ball) to the TBI is threaded and can be adjusted. Could adjusting this quicken the drop out of lockup?

    [/ QUOTE ]

    I'm the one that brought it to the kick down. The problem is NOT with the cruise... Its with the interaction between the cruise, the tthrottle linkage and the TV cable. His problem is not maintaining speed it is maintaining speed go up a hill that requires the transmission to unlock the convetor and/or go down a gear. What functions the unlocking of the convertor and the down shifting of the transmission????? Oh yeah the TV cable is part of that..... OH yeah.... its attached to the throttle linkage..... OH wait a minute let me see oh yes the cruise control is attached to the exact same throttle linkage.

    I NEVER SAID TO ADJUST THE TV CABLE... I just said thats where the problem lies.... It could very well be a loose connection of the TV cable to the throttle linkage.

    The only way the cruise control could be the problem is if the actuator does not have enough travel to open the throttle enough inorder to unlock the tranny via vacuum switch or tv cable to downshift.
     
  19. wadinator

    wadinator 1/2 ton status

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    Jeeze, don't get pissed man! I'm frusterated, but I was never slamming anyone here.

    I see that the cruise, throttle, and tv are all intertwined and work together. I just gotta figure out which one is causing this kickdown issue.

    When I'm losing speed with the cruise on, all I have to do is depress the gas pedal a 1/4 inch for only a second. Then the tranny comes out of lockup and speed resumes to what the cruise is set at before the torque converter locks up again.

    All I need is for that gas pedal to go down that extra 1/4" on it's own, without the aid of my foot.
     
  20. Sidepipes

    Sidepipes 1/2 ton status

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    I'm not pissed.... you wouldn't want to see me pissed.

    Its just the way everybody trashes someones idea before they had even had a chance to comprehend what was said.... I've had it happen to me on here before.

    Everybody thinks they are the expert and that anybody that differs of opinion to them is a retard. I have never claimed to be an expert and I have never trashed anybodies thoughts or opinions.

    I'm thinking its getting near the time to leave here I was hoping this wasn't going to happen but opinions are like assholes, every one has one.... some people just think theirs don't smell.
     

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