I just test drove an 84 Carrera today and I noticed that when the car was idling, it seemed that the engine was cycle-revving - particularly when I pushed in the clutch.

Is this normal? If not, any idea of what the problem is?

Also, what are indications that the car needs a valve adjustment?
TIA

 

I don't think I'd call it "normal," but perhaps "not uncommon" fits. My 86 often does this as well, fluctuating from 1000-1100 rpm.

Do a forum search on "idle" and "idling" and you'll find a myriad of possible faults. The top culprits seem to be:
- idle screw set too high. Adjust to lower idle rpm.
- Head temp sensor needs replacing
- O2 sensor needs replacing
- Idle control valve needs replacing
- Throttle switch needs replacing
- Vacuum leak due to a cracked hose. Locate and replace. (a porsche mechanic told me to slowly spray carb cleaner at joints then if the car stalls, you found it. An unverified tip.)

Good luck, and be sure to post your fix!

Eric

 

My 88 was doing this and it turned out to be the O2 sensor. You can easily clean out the idle control valve and see if that helps any.
Noisy valves usually indicate valve adj. is needed but not always. When was the last time they were done?
Good Luck
Buck 88 Coupe