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Odd cruise control behavior


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I seldom drive my '95 CS convertible (3.1L) on the interstate but I did last night, coming home from a friend's since it was too cool out to put the top down as I had done earlier in the day. When I put the cruise control on, I noticed a very strange phenomenon. As soon as I pressed the button in the end of the turn signal stalk, the throttle opened up and sustained almost 3,500 RPMs. When I disengaged the cruise, I could maintain pretty much the same speed at a little over 2,000 RPMs. Either way, it sort of felt like it might not be going into fourth gear. The shift indicator is messed up so that it shows neutral when I'm in overdrive and overdrive when It's in third. I've gotten used to pulling the shifter back to the detente that should be overdrive, then nudging it forward a notch to actually put it in overdrive and just kind of feeling for reverse since the indicator doesn't show anything for reverse but shows reverse for neutral. The car has a rebuilt transmission with just a couple thousand miles on it. I'd hate to think it's already going bad.

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  • 2 weeks later...

How many times have you tried using cruise control since the transmission rebuild?  Was this the first time this occurred while using cruise control and since the rebuild?

Was your shift indicator always like that, or only since the rebuild?

Is your "SERVICE ENGINE SOON" light on?

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I've used the cruise control several times since the rebuild. Sometimes it works just fine and sometimes it doesn't work at all. Turning the engine off and starting it again seems to reset it. I drove the car today for the first time since I started this thread and it worked with no problems. The shift indicator has always been a little off. Before the rebuild, Drive would actually be Third but the issue with reverse and neutral started after the rebuild and seems to be getting a bit worse. At some point, I need to take it back to the transmission shop and see if they can fix it. The rebuild has a three-year, 30,000 mile warranty so hopefully they can do something. 

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The park-neutral position switch (PNP) could be the culprit with both the shift indicator being "off," as you describe, and causing the erratic shifting behavior.  Now, I'm not 100% on a 1995 vehicle, but the cruise control could be vacuum operated like it is in the older W-bodies.  If you have a disconnected or damaged vacuum line under the hood, it could cause the cruise to fail to operate.

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