johnhassell

Hello all,
Have searched the forums to no avail to find a fix for the following problem. My 83SC's cruise control seems to cycle very regularly about 175-200 rpm even on flat level highways. can't seem to find any suggestions on how to cure this behavior. Any suggestions?
Thanks,
j

Peter Zimmermann

John: Your symptom is, believe it or not, normal. I've never liked the surging, but it's there to stay.
Pete

oto60

Just remove the cruise.

v8_ranch

Wow,

I have had the same question regarding my 83 cab. So it is like this from the factory! I never use it much, but every once in awhile on longer trips it would be nice - but the constant 5 mph cycling is not very desirable... So no fixes eh? (other than to not use)

Lorenfb

The cruise control system was improved when the vacuum controlled actuator was
replaced by a motor driven actuator with feedback on the late 911 3.2s ('87-'89).
The vacuum system still should be fairly stable with a good cruise control unit with
barely noticeable surging which is greater at low speeds (<50MPH) and not at all
noticeable above 60-70MPH. If this is not the case, the cruise control unit may
be bad.

Peter Zimmermann

v8: Correct, it's an awful system. I drove SCs when they were new (we did the first minor service on many of them between 3K and 5K miles), and after inquiries to Porsche, etc., determined that the system is really only good for giving your right leg a short break on long drives. I diagnosed my '82 and had the CC ECU reconditioned, but only because I wanted all of the on-board systems to work, not because I use it!
Pete

Tippy

If it makes you feel better my 996 fluctuates 5 mph also. Set it to say 65 mph, you will get 63-64 mph uphill and 66-67 downhill, of course it isnt cyclic though on flat roads like the SCs. Every other car I have owned outside of Porsche would hold speed dead on.

johnhassell

Thanks for the replies.
Guess I'll just have to learn to live with it. (or just take nice twisty roads to my destinations & leave the 3 hour instate blasts to the SUV/BUF crowd.)

j

glenncof

I've wonder about this for more than 10 years on my 1985. Seems like it would waste lots of gas aside from being an bother. The only time I have used it was to see if it is still working. Cross that off the 'consider' project list. Thanks.

madmmac

Mine also surged a good bit....this is what I did and it made it pretty much perfect.

Make sure all the vacumn hoses, fittings are not leaking or semi plugged up. Once they have been fixed or not, mine were all fine, I pulled the line coming into the vacumn unit and shot some WD40 in it. Shot a bit in the front where the cable comes out to head to the throttle just because and it worked just fine.

The speed became pretty darn stable and the more it got used, the better it seemed to get....that was until the 23 year old cable broke!!

If anyone has one laying around, I'd be glad to buy it from them.

Corrales911

What amuses me about the CC is that when it kicks in the gas it does it with "authority".

glenncof

""What amuses me about the CC is that when it kicks in the gas it does it with "authority".""

Yea, just like the way my wife drives...