Cruise Control 1987 300D Turbo
 

Cruise Control seems to "slip". Control starts to slip then grab, slip then grab after a few minutes at whatever speed the control is set to. Sometimes it will regain the lost speed, moving back to the original setting and other times it simply continues to decline.

Is this the computer or the linkage on the side on the engine that needs to be replaced? The switch on the columen was replaced last year (2000) by Bird Imports in McAllen Texas. They have always done an excellent job with my car, but now I'm in Virginia and not Texas so I'm on my own.

Any help is appreciated

Ditto for me.

The additional disappointing thing about the control is that on encountering a grade the response is almost viscous; leading to hunting. On the level it does very well. It's almost as if the desire for "German" perfection states, "We have a deviation and it will be corrected immediately!"

Dealers have given upon it.

www.gdl-online.com

This is the guy to deal with on resolving cruise control issues. But first make sure all of your throttle linkage - from the rotating piece coming away from the firewall to the cruise control unit and down to the fuel injector is clean ald lubed. I used to use ATF but am currently using Marvel Mystery Oil in my lube squirt can. Peter at GDL is very helpful.

I think there's also an anti-surge modification described in the service manual. As I recall, it involves adding a switchover valve into the line which feeds the ALDA. When cruise is activated, the switchover valve changes the vacuum/boost path such that it passes through a restrictive orifice and/or surge damper. The effect is to delay throttle response - the ALDA doesn't add or remove fuel so quickly, smoothing things out.

I've an '87 300TDT and don't particularly have any complaints about the cruise. Well, it does drop out once in a while - guess I should lube the throttle linkage. Of course, it's so durn flat here in Texas the throttle never gets moved to maintain speed anyway...

- Jim