Georgia Fiero Club Forum

All Things Fiero => Tech Tips, Tech Questions => Topic started by: GTRS Fiero on October 15, 2020, 07:00:38 pm

Title: Falling off cruise
Post by: GTRS Fiero on October 15, 2020, 07:00:38 pm
It has happened, before, but my Fiero is falling off cruise control.  The frequency that this occurs is increasing.  It had happened, but maybe once in 500 miles.  Now, it can happen 8 times in 20 miles.

I am guessing a short, but no idea where to look.
Title: Re: Falling off cruise
Post by: Fierofool on October 15, 2020, 07:28:20 pm
My cruise problems were rust holes in the vacuum canister on one  and a failing dump solenoid on another.  Once after working under the dash I had to readjust the cruise switch on one of the pedals.  I had done something that made it too sensitive.
Title: Re: Falling off cruise
Post by: GTRS Fiero on October 15, 2020, 07:32:41 pm
Well, mine has a digital cruise control, so no canister or dump solenoid.  It could be the brake switch at the pedal.  No clutch on mine.
Title: Re: Falling off cruise
Post by: scottb on October 15, 2020, 09:39:21 pm
Push it to the floor and leave it there...... shouldn't fall off then
Title: Re: Falling off cruise
Post by: GTRS Fiero on October 15, 2020, 09:46:12 pm
Well, guys with guns....you test that for me.  I'm sure you'll do fine.
Title: Re: Falling off cruise
Post by: GTRS Fiero on November 02, 2020, 07:59:43 am
Could my cruise issue be related to the vacuum leak?  I know my cruise is digital, but maybe somehow it feels that things aren't right, and kills the cruise.

Twice, I heard a sound when the cruise disengaged.
Title: Re: Falling off cruise
Post by: Fierofool on November 02, 2020, 10:29:58 pm
Do you want me to send you my base?  You can try it and see if it solves the problem.  If it does, you could have a machine shop do a very light flycut on yours to resurface it.  Then send mine back to me. 
Title: Re: Falling off cruise
Post by: GTRS Fiero on November 02, 2020, 10:33:07 pm
No idea what a flycut is.  I have 2 other bases.  It did the same thing with them.  The issue is the surface of the crossover pipe.
Title: Re: Falling off cruise
Post by: Wreck It Ralph on November 02, 2020, 10:42:33 pm
I would try that Permatex only like we discussed and if not try the groove and ring it. But might be best to get the crossover pipe off. Have it resurfaced and reassemble it off the car. Maybe even ditch the studs for bolts. If it wasn’t for cleaning and two dissimilar metals I’d say weld the base on or have a good machine shop make one out of steel and weld it on.
Title: Re: Falling off cruise
Post by: Fierofool on November 02, 2020, 10:59:02 pm
Flycut is a tool used on a milling machine to impart a very smooth cut surface on a metal.  The smoothness of the finish depends upon the speed of travel of the bed as it passes underneath the flycut tool.  It's a disk with carbide cutting bits attached.

https://www.wisegeek.com/what-is-a-fly-cutter.htm
Title: Re: Falling off cruise
Post by: GTRS Fiero on November 03, 2020, 05:13:32 pm
The Permatex was the red stuff that melted and glopped all over everywhere.
Title: Re: Falling off cruise
Post by: Wreck It Ralph on November 03, 2020, 05:24:34 pm
Did you use the correct one? Red will not withstand that kind of temperature.
Title: Re: Falling off cruise
Post by: GTRS Fiero on November 05, 2020, 09:27:03 pm
I purchased a tube.  We'll see if it works, or not, once it arrives.

There is a construction tent over by the hospital that I plan to appropriate to do this without the Gestapo bothering me.
Title: Re: Falling off cruise
Post by: Wreck It Ralph on November 05, 2020, 09:42:59 pm
Fingers crossed for you.
Title: Re: Falling off cruise
Post by: GTRS Fiero on November 18, 2020, 10:50:50 pm
Now, my cruise isn't working, at all.  I'm going to try a new stalk.
Title: Re: Falling off cruise
Post by: GTRS Fiero on April 03, 2021, 11:20:15 am
New stalk, no change.

Tested every pin on the connector.  Each pin works as expected, other than the VSS.  For the VSS pin, there is no voltage.  Even while the vehicle is moving, nothing.  I suspect a scope is required, but I don't have one.  Certainly, nothing shows on a digital multi-meter.  Any way to test the VSS signal?
Title: Re: Falling off cruise
Post by: Fierofool on April 03, 2021, 04:37:57 pm
I had a cruise problem on one of my 85's.  The cruise would set, but then it would gradually fall off.  Sometimes it would recover and accelerate wildly.  I found that the vacuum canister had rusted through on the bottom surface where it wasn't readily available.  I know yours is a digital cruise, but does it use a vacuum in any way? 
Title: Re: Falling off cruise
Post by: GTRS Fiero on April 03, 2021, 04:42:28 pm
Nope.  No vacuum.
Title: Re: Falling off cruise
Post by: GTRS Fiero on April 29, 2021, 06:35:53 pm
Well, it has totally fallen.  Fallen cruise.  I suspect that either the bridge failed, or the wiring between the ECU and the cruise module is electrically distancing.