Cruise Control is Jumpy...

So I'm driving to Bryan Texas yesturday for work and I set the cruise control, in my 85 300TD to 75mph. It hold the speed fine. But after about 15mins or so it start to speed up, and then slow down...kind of jumpy.

It got worse over time until I finally got tired of getting my head knocked around to where I turn the cruise control off. Everything else with the cruise control works, (de) accelerate, on, and off, but it just can't hold the same speed. Everything else in the car works, no vacuum leaks, speedometer is fine, everything. (knock on wood...)

Any suggestions? Should I resolder the cruise amp?

Jason

Before trying anything else, lubricate the cable between the server and the throttle linkage.

Good luck,

Graphite?

[lrg]

Larry,
The later cars don't have a cable, just additional linkage from the electric actuator.

Benzzy, to Larry's point you still want to eliminate that as a potential cause since it's easy and costs almost nothing. Pull apart the little ball joints on the linkage one by one and clean and relube then. I usually use a small dab of lithium lube and it's probably a good idea to do them all, not just the ones to the cc. Unless your linkage is really dried out my guess is that won't fix it and if that is the case the next easy and inexpensive step is to clean up all the electrical connections. If it's it's still not right do a search here for some diagnostic tests to be sure it's the amp (actually available on GDL's website). If that finally proves to be the culprit then resoldering may be your next step. Unfortunately that doesn't always work and you may end up having to decide if a rebuilt unit is worth the cost. Let us know what happens.

Duh...

Yes I know that the newer cars are drive by wire and the computer sends the throttle position signal to the throttle actuator. He asked specifically, however, regarding his '85 300D. Unless there's been a retrofit that I'm not aware of, these are not fly by wire throttle systems.

Have a great day,

[lrg]

Larry,
My point exactly. Unless his '85 300D is very different than mine there is no "cable" between the CC actuator (I assume that's what you meant by "server") and the actual linkage to the IP. The earlier (pre '82?) cars had a cable from a servo (vacuum powered?) that I believe was mounted on the fender. The drive by wire system came much later. The late 123s and early 124s connected the actuator to the IP linkage with additional linkage, not cable.

By the way, I'm not trying to give you a hard time, just trying to clarify things.

LRG

LOL! I am laughing my butt off at myself!

I do software application development and support for an extensive Client/Server based software package. All day long I think in terms of clients and servers so server is one of those things that dance in my mind.

When I meant to write SERVO, I wrote SERVER!



Back to the topic. So that particular model has mechanical linkage instead of a cable? Okay, fine, so lube the linkage instead of the cable! Geez!

Have a great day,

I think I got it, and I think it is good advice.

In fact I probably to lube the entire throttle linkage while I'm at it. I have notice it has been a little sticky.

I let you know the results...

Thanks Jason