Ok,

It took a couple days to get to, but I finally got around to playing with the cruise control yesterday. I cleaned all of the connections I could find and checked the throttle linkages then took it for a test drive - same jerky symptoms continued. Then I pulled the gauge cluster and worked some liquid graphite lube into the speedo cable and replaced my speed sensor on the back of the speedometer with one from a 1988 300e (I read that this part was superceded sometime in 1987 and indeed the spare on my shelf was just slightly different than the original).

My speedo is now very solid and my cruise is 99% smoother. It did make one jerk on the test drive so I won't say 100%.

I won't be completely comfortable that it's fixed until I try it out for something more than a test drive, but there is a very big difference from the previous test drives.

Earlier this week I spent time working on the speedo cables on my '76 GMC pickup. The speedometer was swinging pretty severely at any speed less than 50mph and the swings would be about +- 20mph. I could even hear the cable binding when I'd drive it. On that vehicle I was able to pull the cable cores out (there are 2), clean them and lube them with liquid graphite lube (even my NAPA store no longer carries anything labeled speedometer cable lubricant). The speedometer is now rock solid.

The MB was just very slightly wobbling below about 50mph. Sadly I couldn't pull the core out of the 300e cable (I tried from both ends). I was able to work a little lube into the cable from the top and it certainly helped the stability of the speedometer. Since there is some flex in the cable I would have to disagree that the cable could not affect the operation of the cruise control. If the speed sensor senses something being turned by that cable and the cable is binding (therefore slowing down as it binds, then speeding up as it frees up) then it seems logical that it could affect the smoothness of the speed control - and being a Mercedes the cruise has to be EXACT and precise so I'm guessing that it was trying to chase the cable.

I hope that's it because I REALLY DONT LIKE pulling that cruise amp.

Hope that helps all.

By the way, xtreme barton, I feel EXACTLY as you do. This car seems to be one thing after another and I'm getting a lot of wrench time on it. But it could be worse - it could be a Volkswagen. I'm ready to park ours in a questionable neighborhood and leave the keys on the dash of ours....but that's another story!

__________________
Bob Kopicki
Massillon OH
'97 VW Cabrio (POS)
'93 Miata
'87 300e
'76 GMC C-15
'67 TR-4a

well im gonna try and tackle my speedometer here in the next few days .. its kinda a pain but its worth it in the end i guess .. i always feel like i got something accomplished .. unfortunately ive been pretty anal about fixing every little thing i can find .. maybe im just bored