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Cruise Control issues

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Anybody have ideas on this little problem? My cruise control surges, meaning it will hold speed, but as you are at highway speeds it will vary rpm roughly every 5 seconds. This gets to be REALLY annoying when on a 6 hour trip.... I have not done any trouble shooting yet, just wondering if anyone else has had this. Thanks, Chris

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Not sure if you guys have the vacuum actuated cruise control or not. If the vacuum lines have any leak at all, the cruise control will act very weird. This can be hard to chase since mine was acting weird but when you hooked a vacuum gauge on it, I was seeing 30" Hg just idling.. But I ignored that and got new vacuum line connectors and even got some of those tiny little compression clamps to ensure everything was sealed. My cruise is very very smooth now. If you go out to your truck after you have shut it off, you can pull one of the caps off like I show in the pic and it should have vacuum even after a day of sitting. Another way to check it is to turn the truck to the vents that blow air on your head, go back out later and turn the key on but don't start the truck, turn the blower on and it should still be blowing through those vents, if it loses vacuum, it will have defaulted back to the defrost since that uses no vacuum. You can also hook a vacuum gauge up to it and come back after a while.

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    I was thinking the same thing as ISX.. So I wont re-type it :cool:

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    Hey ISX, Thanks for your input, I am going to check this in a few days and see what I find. I remember one short piece of vacuum line that looked pretty dried out, so i'll start there first. Thanks, Chris

    Not sure if you guys have the vacuum actuated cruise control or not. If the vacuum lines have any leak at all, the cruise control will act very weird. This can be hard to chase since mine was acting weird but when you hooked a vacuum gauge on it, I was seeing 30" Hg just idling.. But I ignored that and got new vacuum line connectors and even got some of those tiny little compression clamps to ensure everything was sealed. My cruise is very very smooth now. If you go out to your truck after you have shut it off, you can pull one of the caps off like I show in the pic and it should have vacuum even after a day of sitting. Another way to check it is to turn the truck to the vents that blow air on your head, go back out later and turn the key on but don't start the truck, turn the blower on and it should still be blowing through those vents, if it loses vacuum, it will have defaulted back to the defrost since that uses no vacuum. You can also hook a vacuum gauge up to it and come back after a while.

    what isx said the servo could be bad..unhooked..maybe need to spray some wd40 on the cruise cable underneath the black cover.it may have a dry spot on it where it would hung up.

    Not sure if you guys have the vacuum actuated cruise control or not. If the vacuum lines have any leak at all, the cruise control will act very weird. This can be hard to chase since mine was acting weird but when you hooked a vacuum gauge on it, I was seeing 30" Hg just idling.. But I ignored that and got new vacuum line connectors and even got some of those tiny little compression clamps to ensure everything was sealed. My cruise is very very smooth now. If you go out to your truck after you have shut it off, you can pull one of the caps off like I show in the pic and it should have vacuum even after a day of sitting. Another way to check it is to turn the truck to the vents that blow air on your head, go back out later and turn the key on but don't start the truck, turn the blower on and it should still be blowing through those vents, if it loses vacuum, it will have defaulted back to the defrost since that uses no vacuum. You can also hook a vacuum gauge up to it and come back after a while.

    hay...what is that little disk in front of the red clamp?debris filter?vac. filter?can i get on at o'reillys or autozone?and..the hose before and after it are brittle and heat beaten i guess...can i get your:2cents: plz!!:smart:

    That's a check valve, you can get it from any auto parts store. I don't have much trust in the vacuum pump or anything so I put that in there to keep any vacuum that goes into the HVAC from going back out. Works so good I can put it on head vents and come back a few days later and turn the key on (not starting engine), turn the blower motor on, and it will still be on the head vents. Neatest thing I ever bought for the truck :lol: Think it was only a couple bucks.

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    That's a check valve, you can get it from any auto parts store. I don't have much trust in the vacuum pump or anything so I put that in there to keep any vacuum that goes into the HVAC from going back out. Works so good I can put it on head vents and come back a few days later and turn the key on (not starting engine), turn the blower motor on, and it will still be on the head vents. Neatest thing I ever bought for the truck :lol: Think it was only a couple bucks.

    sweeeeeeet..thank ya...my truck has one on it from the factory..gunna replace it and those short run of hoses.
    • Author

    Isx, Where did you get your clamps? I replaced several pieces of line, cruise is much better but still just a little surge... I figure I just need a little more work. GB

    Not sure if you guys have the vacuum actuated cruise control or not. If the vacuum lines have any leak at all, the cruise control will act very weird. This can be hard to chase since mine was acting weird but when you hooked a vacuum gauge on it, I was seeing 30" Hg just idling.. But I ignored that and got new vacuum line connectors and even got some of those tiny little compression clamps to ensure everything was sealed. My cruise is very very smooth now. If you go out to your truck after you have shut it off, you can pull one of the caps off like I show in the pic and it should have vacuum even after a day of sitting. Another way to check it is to turn the truck to the vents that blow air on your head, go back out later and turn the key on but don't start the truck, turn the blower on and it should still be blowing through those vents, if it loses vacuum, it will have defaulted back to the defrost since that uses no vacuum. You can also hook a vacuum gauge up to it and come back after a while.

    NAPA. I would think any auto place would have them. Just tell them you want some compression clamps. Not sure if thats what they are called but sounds good :lol: They come in all different sizes, you can see the red one is bigger than the silver ones, so make sure you get the right ones. I think the check valve is what really did it. I didn't replace any lines, just some of the fittings and I think the vacuum pump has times when it becomes flakey, so the check valve ensures that the HVAC or cruise control doesn't know the difference. Either way, the clamps or the check valve solved all of my vacuum issues.

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    Thanks, I purchased a new check valve because my original leaked by a bit. My new one seems to be the same. Do these leak by a little on purpose or should they only allow flow one way? Seem to me my new one is faulty. GB

    NAPA. I would think any auto place would have them. Just tell them you want some compression clamps. Not sure if thats what they are called but sounds good :lol: They come in all different sizes, you can see the red one is bigger than the silver ones, so make sure you get the right ones. I think the check valve is what really did it. I didn't replace any lines, just some of the fittings and I think the vacuum pump has times when it becomes flakey, so the check valve ensures that the HVAC or cruise control doesn't know the difference. Either way, the clamps or the check valve solved all of my vacuum issues.

    They shouldn't leak at all. I can go back to mine days later after leaving it on head vents, and it will still be on head vents before the engine even starts. You sure it's the check valve leaking and not something else?

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    I was able to apply a vacuum with my calibrated lungs and determined that they both leak by. I just purchased a second replacement check valve, and lo... it actually functions as a check valve should. GB

    They shouldn't leak at all. I can go back to mine days later after leaving it on head vents, and it will still be on head vents before the engine even starts. You sure it's the check valve leaking and not something else?

    I was able to apply a vacuum with my calibrated lungs and determined that they both leak by. I just purchased a second replacement check valve, and lo... it actually functions as a check valve should.

    GB

    Yes, calibrated lungs help :lol: I was at the store today and eyeing all of the push in connectors with all the hard plastic line... Thinking that would be the hot setup. Let me save some more pennies up and maybe one day I will do it. :spend:

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    Not sure if you guys have the vacuum actuated cruise control or not. If the vacuum lines have any leak at all, the cruise control will act very weird. This can be hard to chase since mine was acting weird but when you hooked a vacuum gauge on it, I was seeing 30" Hg just idling.. But I ignored that and got new vacuum line connectors and even got some of those tiny little compression clamps to ensure everything was sealed. My cruise is very very smooth now. If you go out to your truck after you have shut it off, you can pull one of the caps off like I show in the pic and it should have vacuum even after a day of sitting. Another way to check it is to turn the truck to the vents that blow air on your head, go back out later and turn the key on but don't start the truck, turn the blower on and it should still be blowing through those vents, if it loses vacuum, it will have defaulted back to the defrost since that uses no vacuum. You can also hook a vacuum gauge up to it and come back after a while.

    ok..went to o'reillys today and got the vacuum check valve.it is one of those items hanginh on the self in the HELP section....part number is 47149 and replaced both hose on each side.they were really cracked/dry rotted.:thumbup2:
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