I recently just purchased a 1983 300D in fantastic condition. Today on the interstate, I noticed that when I set the cruise control, the engine felt like it was having some hesitations, back and forth. If I deactivate cruise control, the engine runs fine, no problems what so ever.

Does anyone have any ideas regarding this issue? Thanks in advance!

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1985 300SD - 167k miles
1992 F350 7.3 (Soon to be converted to 2 tank Veggy/WMO)

http://www.peachparts.com/shopforum/search.php?searchid=1818147

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

First thing I would do is lube up all the linkage joints to make it a bit easier on the CC. You also need to remove any excess play in the linkage.

Then the CC will still do the same thing! They are just too precise...they are speed control, not cruise control. My MB will hold the speed perfect, uphill or downhill while my Chevy says "want the heck" and will vary 2 to 4 mph. That may be what you are feeling...took me a while to get used to it.

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day

Link does not seem to work?

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1985 300SD - 167k miles
1992 F350 7.3 (Soon to be converted to 2 tank Veggy/WMO)

Mark, thanks for your reply. I will try to do that later this week. Will let you know if I have any further questions!

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1985 300SD - 167k miles
1992 F350 7.3 (Soon to be converted to 2 tank Veggy/WMO)

The variance of speed while using the cruise control is not engine related at all. Its due to the cruise control amplifier being worn out/having bad components in it due to age, and thus it doesn't operate as precise as it should...it compensates for hills too much (or even on flat ground) and moves the throttle too much either way, causing that "power/no power" feeling. A perfect working MB cruise system is so precise and smooth that you will never see the speedo move even up or down steep slopes....its quite amazing.

While a precise and awesome system, the MB cruise amps are not known for their long-term reliability. Its expen$ive to keep them in proper order.

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I agree, when they are correct they work very smoothly. Mine was getting a little glitchy, so I replaced both the actuator and amplifier a few months ago (from GDL). Now it works like new.

In my experience, this is an indication of the amp beginning to fail.

But, lube the linkage first, that's free!

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

can the amp be opened up and resoldered like the acc? I've never been able to remove one from under the dash to try.

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the sooner you start... the sooner you'll get done If it ain't broke, don't fix it.. Its always simpler to tell the truth...
2007 Honda Accord EX
2007 Honda Accord SE V6
96 C220
97 Explorer - Found Another Home
2000 Honda Accord V6 - Found Another Home
85 300D - Found Another Home
84 300D - Found Another Home
80 300TD - Found Another Home
Previous cars:
96 Caravan
87 Camry
84 Cressida
82 Vanagon
80 Fiesta
78 Nova
Ford Cortina
Opel Kadet
68 Kombi
Contessa

Thanks again for everyone's input. How much are the CC Amplifier parts? I will try lubing the links tonight.

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1985 300SD - 167k miles
1992 F350 7.3 (Soon to be converted to 2 tank Veggy/WMO)

First of all congratulations on finally picking a car. Can you PM me on the 240 you were looking at if it's still available?

The cruise control uses a feedback mechanism to determine the position of the arm on the actuator. The amp (or controller, or whatever you want to call it) under the dash turns on an electric motor in the actuator and engages a clutch to move the arm and figures out how much the arm moved by a variable resistor in the actuator. The resistor is made up of two resistive tracks on the circuit board and a contact on the bottom of one of the gears that moves up and down the track. As the position of the gear changes so does the resistance value. The grease on the gears in the actuator tends to sling around in there and coat the tracks on the circuit board which throws off resistance value. The amp can no longer tell the position of the arm with much accuracy and tends to overshoot until the vehicle gets enough above or below the target speed that is compensates. The end result is the speed hunts around that target speed instead of staying steady.

For detailed cruise control testing steps check out the procedures here-
http://gdl-online.com/testproc.html. GDL also sells rebuilt amps and actuators if you need one unless you've tried to repair yours already.

If you are a do it yourself-er you can open up the actuator case and use a qtip and some contact cleaner to degrease the resistive traces on the board then clean and relube the gears. Whatever you do don't spray contact cleaner into the actuator housing because you'll wash out whatever lubrication is left on the armature bushing under the circuit board. For the amp you can resolder the connections and replace the capacitors for good measure. Those two things will clear up a suprising number of problems.