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850 cruise control - holds speed 5 MPH slower than set speed 850 1995


Got an odd problem with the cruise control in a '95 850. I've read many posts about 850 cruise control problems, most dealing with a broken vacuum hose under the battery. I found and fixed that issue but my car's problem did not go away.

Here's what it does:

1. When the cruise control is set, the car's speed drops about 4, maybe 5 MPH, then the cruise holds at that speed. Example: if driving at 75 and set the CC, the car coasts until it gets down to about 71, then the cruise maintains speed. I believe it works fine maintaining the slower speed (getting this information second-hand from son who is driving the car to school).

2. When using the "slow down" function (button on end of turn signal pushed down), the car will slow as it should, but when the button is released it drops another 4-5 MPH and holds that speed. Pretty much the same as (1) above, except using the slow down function instead of the initial CC set function. In both cases, the cruise maintains a speed about 5 MPH below where it should.

3. "Resume speed" does not work. Can feel the gas pedal move when resume is "engaged", but within about a second the cruise disengages. Of specific interest, it does _not_ resume and hold a speed 5 MPH below the previous set speed. If resume is engaged repeatedly, each time the gas pedal moves as if trying to reset the cruise, but it quits trying after a second.

Hopes were high when I found the broken vacuum line under the battery tray - I thought I had an easy, cheap fix using a "textbook" brickboard solution. Unfortunately this one didn't go away quite so easily.

Any help appreciated,

Terry








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    850 cruise control - holds speed 5 MPH slower than set speed 850 1995

    I know it has been many years since you asked about this problem. But if by chance you still have the same email as back then, what did you find out to be the actual problem? I have the exact three symptoms and have been struggling with this for a while. The loss of 5 mph was caused by a vacuum leak under battery tray. But the lack of resume and Set + acceleration functionality still plagues me. Even after I substituted out the control module. Only speed signal comes to mind, because sometimes it sets fine, but then the resume and Set + will then follow and not work.








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    850 cruise control - holds speed 5 MPH slower than set speed 850 1995

    Often the circumstances of setting the cruise speed will alter the setting...if you set it on a slight up or downhill grade, the car speeds up or slows down during the few seconds while the vaccum kicks in and seeks the appropriate pedal position. I find it's more accurate on flat ground, and if you don't remove your foot from the accelerator but let the accelerator fall away on it's own.








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    850 cruise control - holds speed 5 MPH slower than set speed 850 1995

    I had similar problems in my 1995 base 850. It turned out to be the very same vacuum line you spoke of and where it connected to the accelerator - it helped to have someone jam their head under the dash to check motion of the pedal & listen for leaks while I sucked on the vacuum line.







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